Introduction

NOTE: For Specifications with illustrations, make reference to Engine Specifications For G379, G398 & G399 Engines, Form No. REG01306. If the Specifications in Form REG01306 are not the same as in the Systems Operation and the Testing and Adjusting, look at the printing date on the back cover of each book. Use the Specifications given in the book with the latest date.

Troubleshooting

Troubleshooting can be difficult. On the following pages there is a list of possible problems. To make a repair to a problem, make reference to the cause and correction.

This list of problems, causes, and corrections, will only give an indication of where a possible problem can be, and what repairs are needed. Normally, more or other repair work is needed beyond the recommendations in the list. Remember that a problem is not normally caused only by one part, but by the relation of one part with other parts. This list cannot give all possible problems and corrections. The serviceman must find the problem and its source, then make the necessary repairs.

Troubleshooting Index

1. Engine Will Not Turn When Start Switch Is On.

2. Engine Will Not Start.

3. Misfiring Or Running Rough.

4. Stall At Low rpm.

5. Sudden Changes In Engine Speed (rpm).

6. Not Enough Power.

7. Too Much Vibration.

8. Loud Combustion Noise.

9. Loud Noise (Clicking) From Valve Compartment.

10. Oil In Cooling System.

11. Mechanical Noise (Knock) In Engine.

12. Gas Consumption Too High.

13. Loud Noise From Valves Or Valve Drive Components.

14. Little Movement Of Rocker Arm And Too Much Valve Clearance.

15. Valve Rotocoil Or Spring Lock Is Free.

16. Oil At The Exhaust.

17. Little Or No Valve Clearance.

18. Engine Has Early Wear.

19. Coolant In Lubrication Oil.

20. Exhaust Temperature Is Too High.

21. Engine Has Low Oil Pressure.

22. Engine Uses Too Much Lubrication Oil.

23. Engine Coolant Is Too Hot.

24. Starter Motor Does Not Turn.

25. Alternator Gives No Charge.

26. Alternator Charge Rate Is Low Or Not Regular.

27. Alternator Charge Too High.

28. Alternator Has Noise.

29. Short Spark Plug Life.

30. Pre-Ignition.

31. Detonation.

32. Gas Supply Line Shutoff Valve Failure.

33. Instrument Panel Gauge Switches Do Not Stop Engine.

34. Instrument Panel Gauge Switches Prevent Engine Start.

35. Failure Of Overspeed Contactor Switch To Shutoff Engine.

36. Overspeed Contactor Stops Engine At Low Speed.

37. Solid State Magneto (Altronic).

Problem 1: Engine Crankshaft Will Not Turn When Start Switch Is On

Probable Cause:

1. Battery Has Low Output:

Make reference to Problem 24.

2. Wiring Or Switches Have Defect:

Make reference to Problem 24.

3. Prelube Pump Switch Has A Defect:

Check prelube system for malfunction. Repair or replace components as necessary.

4. Starter Motor Solenoid Has A Defect:

Make reference to Problem 24.

5. Starter Motor Has A Defect:

Make reference to Problem 24.

6. Inside Problem Prevents Engine Crankshaft From Turning:

If the crankshaft cannot be turned after disconnecting the driven equipment, remove the spark plugs and check for fluid in the cylinders while turning the crankshaft. If fluid in the cylinders is not the problem, the engine must be disassembled to check for other inside problems. Some of these inside problems are bearing seizure, piston seizure, wrong pistons installed in the engine, and valves making contact with pistons.

Problem 2: Engine Will Not Start

Probable Cause:

1. No Gas To Engine:

Check gas supply and pressure regulator. Reset shutoff valve in the supply line. Check carburetor throttle, and linkage between carburetor and governor.

2. Wrong Ignition Timing:

Time magneto to engine.

3. Timing Failure:

Check the ignition transformers for loose connection, moisture, short or open circuits. Check the low and high tension wiring. Check the spark plugs for correct type and spark plug adapters. Check the magneto. Repair or replace any component that shows signs of failure.

4. Gas Line Pressure Regulator Not Working:

Clean balance line. Check inlet and outlet regulator pressures.

5. Carburetor Not Working:

Check all carburetor adjustments. Be sure that throttle plate is open and that governor permits it to open fully. Check the BTU content of the fuel based on lower heat value (LHV). If it is too low, a higher fuel pressure (correct spring in the regulator), or a special carburetor may be needed. Inspect the fuel-air diaphragm for leaks, dirt or wet fuel. Check the governor high idle and carburetor stop screw for low idle adjustments.

6. Slow Cranking Speed:

Cranking speed must be at least 150 rpm. Check condition of starting system. See Problem 24.

7. Switch Of The Gauge Panel Broken:

Hold in reset button of the magnetic switch while cranking to cut out (override) gauge switches.

Problem 3: Misfiring Or Running Rough

Probable Cause:

1. Ignition Failure:

Make reference to Problem 2.

2. Low Gas Pressure:

Check for leaks in gas supply. Check the line pressure regulator, shutoff valve and solenoid. If two or more engines are used, be sure the common supply line is large enough. Regulator pressure should not change over the normal load range. Inspect the regulator diaphragm for leaks and valve for correct seat contact. Check gas pressure before and after the line pressure regulator. Check for restriction in balance line from carburetor to regulator. Set valve clearances.

Problem 4: Stalls At Low RPM

Probable Cause:

1. Idle rpm Too Low:

Make adjustment to the throttle stop screw at the carburetor.

2. Too Much Load:

Check for attachment excessive loading. Reduce load and/or adjust throttle stop. If necessary, disconnect attachments and test engine.

Problem 5: Sudden Changes In Engine Speed (rpm)

Probable Cause:

1. Governor Failure:

Look for damaged or broken springs, linkage or other components. Check governor-to-carburetor linkage or other components. Check for correct spring. Check governor oil pump and bypass valve.

2. Wrong Adjustment Or Leaky Valve:

Make adjustment to the valves.

3. Carburetors Not Balanced (Synchronized):

Make adjustment to balance carburetors (synchronize).

4. Turbocharger Differential Pressure Control Valve Failure:

Inspect the valve. Check valve diaphragm for leakage.

5. Governor Or Linkage Adjustment Incorrect:

Check to see if leakage between governor and carburetor operates smoothly and has no free play. Make adjustment to the governor and linkage as necessary.

Problem 6: Not Enough Power

Probable Cause:

1. Low Gas Pressure Or Gas Line Pressure Regulator Failure:

Make reference to Problem 3.

2. Carburetor Adjustment Or Carburetor Not Working:

Make reference to Problem 2.

3. Leaks In Air Induction System:

Check air cleaner for restriction. Check inlet manifold pressure on turbocharged engines.

4. Governor Control Linkage And/Or Throttle Valve Balance (Synchronized):

Adjust linkage and make adjustment to throttle valve balance (synchronize).

5. Too Much Valve Clearance:

Make adjustments according to the subject, Valve Clearance.

6. Ignition Wiring Failure:

Check for damage to wiring, arcing, or bare wire. Check rubber boot over spark plugs for cracks or moisture.

7. Transformer Failure:

Check for loose connections, moisture, short or open circuits.

8. Bad Spark Plugs:

Check type of plug used. Install correct type. Inspect for gas leaks and/or cracked porcelain. Clean and set gap of the plugs. Install new plugs if badly worn.

9. Wrong Timing:

Time magneto to engine. Tighten any loose wires.

10. Spark plug Adapters Leak:

Check for water leakage into cylinder, or combustion gases in coolant. Install new adapters.

11. Differential Pressure Regulator Failure:

Check the valve movement. Check the diaphragm for leaks.

12. Too Much Carbon In Turbocharger Or Slow Turning:

Inspect and install a new turbocharger as necessary.

13. Deposits In The Combustion Chamber:

Make a compression test on all cylinders. Any cylinder which has great difference from the others should be inspected and cleaned.

Problem 7: Too Much Vibration

Probable Cause:

1. Loose Bolts Or Nuts Holding Pulley Or Damper:

Tighten bolts or nuts.

2. Pulley Or Damper Has A Defect:

Install a new pulley or damper.

3. Engine Supports Are Loose, Worn, Or Have A Defect:

Tighten all mounting bolts. Install new components if necessary.

4. Misfiring Or Running Rough:

Make reference to Problem 3.

Problem 8: Loud Combustion Noise (Sound)

Probable Cause:

1. Gas Octane Rating Too Low:

Use recommended gas.

2. Detonation:

Make reference to Problem 31.

3. Pre-Ignition:

Make reference to Problem 30.

Problem 9: Loud Noise (Clicking) From Valve Compartment

Probable Cause:

1. Broken Valve Spring(s):

Install new parts where necessary. Broken locks can cause the valve to slide into the cylinder. This will cause much damage.

2. Not Enough Lubrication:

Check lubrication in valve compartment. There must be a strong flow of oil at engine high rpm, but only a small flow of oil at low rpm. Oil passages must be clean, especially those sending oil to the cylinder head.

3. Not Enough Valve Clearance:

Make adjustments according to the subject, Valve Clearance.

Problem 10: Oil In Cooling System

Probable Cause:

1. Defect In Core Of Oil Cooler:

Install a new core in the oil cooler.

2. Defect In Head Gasket:

Install a new head gasket.

Problem 11: Mechanical Noise (Knock) In Engine

Probable Cause:

1. Failure Of Bearing For Connecting Rod:

Inspect the bearing for the connecting rod and the bearing surface on the crankshaft. Install new parts where necessary.

2. Damaged Timing Gears:

Install new parts where necessary.

3. Defect In Attachment:

Repair or install new components.

4. Broken Crankshaft:

Install a new crankshaft.

Problem 12: Gas Consumption Too High

Probable Cause:

1. Gas System Leaks:

Replacement of parts is needed at points of leakage.

2. Spark Plugs Not Firing:

Check spark and install new plugs if necessary.

3. Wrong Timing:

Make adjustment to timing.

Problem 13: Loud Noise From Valves Or Valve Drive Components

Probable Cause:

1. Broken Valve Spring(s):

Make replacement of damaged parts.

2. Broken Camshaft:

Make replacement of damaged parts. Clean engine thoroughly.

3. Vibration Damper Has Defect:

Install a new damper.

Problem 14: Little Movement Of Rocker Arm And Too Much Valve Clearance

Probable Cause:

1. Not Enough Lubrication:

Check lubrication in valve compartment. There must be a strong flow of oil at engine high rpm, but only a small flow at low rpm. Oil passage must be clean, especially those sending oil to the cylinder head.

2. Rocker Arm Worn At Face That Contacts End Of Valve:

If there is too much wear, install new rocker arms. Make adjustment of valve clearance according to the subject, Valve Clearance.

3. End Of Valve Stem Worn:

If there is too much wear, install new valves. Make adjustment of valve clearance according to the subject, Valve Clearance.

4. Worn Push Rods:

If there is too much wear, install new push rods. Make adjustment of valve clearance according to the subject, Valve Clearance.

5. Valve Lifters Worn:

If there is too much wear, install new valve lifters. Make adjustment of valve clearance according to the Subject, Valve Clearance.

6. Broken Or Worn Valve Lifters:

Install new valve lifters. Check camshaft for wear. Check for free movement of valves or bent valve stem. Clean engine thoroughly. Make adjustment of valve clearance according to the subject, Valve Clearance.

7. Worn Cams On Camshaft:

Check valve clearance. Check for free movement of valves or bent valve stems. Install a new camshaft. Make adjustment of valve clearance according to the subject, Valve Clearance.

Problem 15: Valve Rotocoil Or Spring Lock If Free

Probable Cause:

1. Broken Locks:

Broken locks can cause the valve to slide into the cylinder. This will cause much damage.

2. Broken Valve Spring(s):

Install new valve spring(s).

Problem 16: Oil At The Exhaust

Probable Cause:

1. Too Much Oil In The Valve Compartment:

Look at both ends of the rocker arm shaft. Be sure that there is a plug in each end.

2. Worn Valve Guides:

Reconditioning of the cylinder head is needed.

3. Worn Piston Rings:

Inspect and install new parts as needed.

4. Turbocharger Leak:

Check turbocharger oil seals.

Problem 17: Little Or No Valve Clearance

Probable Cause:

1. Worn Valve Seat Or Face Of Valve:

Reconditioning of cylinder head is needed. Make adjustment of valve clearance according to the subject, Valve Clearance.

Problem 18: Engine Has Early Wear

Probable Cause:

1. Dirt In Lubrication Oil:

Remove dirty lubrication oil. Install a new oil filter element. Put clean oil in the engine.

2. Air Inlet Leaks:

Inspect all gaskets and connections. Make repairs if leaks are found.

Problem 19: Coolant In Lubrication Oil

Probable Cause:

1. Failure Of Oil Cooler Core:

Install a new core for the oil cooler.

2. Failure Of Cylinder Head Gasket:

Install a new cylinder head gasket. Tighten the bolts that hold the cylinder head, according to the Specifications.

3. Crack Or Defect In Cylinder Head:

Install a new cylinder head.

4. Crack Or Defect In Cylinder Block:

Install a new cylinder block.

Problem 20: Exhaust Temperature Is Too High

Probable Cause:

1. Air Inlet System Has A Leak:

Check pressure in the air inlet manifold. Look for restrictions at the air cleaner. Correct any leaks.

2. Exhaust System Has A Leak:

Find cause of exhaust leak. Make repairs as necessary.

3. Air Inlet Or Exhaust System Has A Restriction:

Remove restriction.

4. Wrong Fuel Injection Timing:

Make an adjustment to the timing.

Problem 21: Engine Has Low Oil Pressure

Probable Cause:

1. Dirty Oil Filter Or Oil Cooler:

Check the operation of bypass valve. Install new oil filter elements if needed. Clean or install new oil cooler core. Remove dirty oil from engine. Put clean oil in engine.

2. Too Much Clearance Between Rocker Arm Shaft And Rocker Arms:

Check lubrication in valve compartment. Install new parts as necessary.

3. Oil Pump Suction Pipe Has A Defect:

Replacement of pipe is needed.

4. Pressure Regulating Valve Does Not Close:

Clean valve and housing. Install new parts as necessary.

5. Oil Pump Has A Defect:

Repair or replace oil pump as necessary.

6. Too Much Clearance Between Crankshaft And Crankshaft Bearings:

Install new crankshaft bearings.

7. Too Much Clearance Between Camshaft And Camshaft Bearings:

Install new camshaft and camshaft bearings if necessary.

8. Defect In Oil Pressure Gauge:

Install new gauge.

Problem 22: Engine Uses Too Much Lubrication Oil

Probable Cause:

1. Too Much Lubricating Oil In Engine:

Remove extra oil. Find where extra oil comes from. Put correct amount of oil in engine. Do not put too much oil in engine.

2. Oil Leaks:

Find all oil leaks. Make repairs as needed.

3. Oil Temperature Is Too High:

Check operation of oil cooler. Install new parts if necessary. Clean the core of the oil cooler.

4. Too Much Oil In Valve Compartment:

Make reference to Problem 16.

5. Worn Valve Guides:

Make reference to Problem 16.

6. Worn Piston Rings:

Install new parts if necessary.

Problem 23: Engine Coolant Is Too Hot

Probable Cause:

1. Restriction To Air Flow Through Radiator Or Restriction To Flow Of Coolant Through The Heat Exchanger:

Remove all restrictions of flow.

2. Not Enough Coolant In System:

Add coolant to cooling system.

3. Pressure Cap Has A Defect:

Check operation of pressure cap. Install a new pressure cap if necessary.

4. Combustion Gases In Coolant:

Find out where gases get into the cooling system. Make repairs as needed.

5. Water Temperature Regulators (Thermostats) Or Temperature Gauge Has A Defect:

Check water temperature regulators for correct operation. Check temperature gauge operation. Install new parts as necessary.

6. Water Pump Has A Defect:

Install a new water pump.

7. Too Much Load On The System:

Reduce the load.

8. Wrong Timing:

Make adjustment to timing.

Problem 24: Starter Motor Does Not Turn

Probable Cause:

1. Battery Has Low Output:

Check condition of battery. Charge battery or make replacement as necessary.

2. Wiring Or Switch Have Defect:

Make repairs or replacement as necessary.

3. Starter Motor Solenoid Has A Defect:

Install a new solenoid.

4. Starter Motor Has A Defect:

Make repair or replacement of starter motor.

5. Prelube Oil Pressure Switch Has Defect:

Check the switch and make replacement if necessary.

6. Prelube System Relay Has A Defect:

Check the relay and make replacement as necessary.

7. Inside Of Engine Problem:

Make reference to Problem 1.

Problem 25: Alternator Gives No Charge

Probable Cause:

1. Loose Drive Belt For Alternator:

Make an adjustment to put the correct tension on the drive belt.

2. Charging Or Ground Return Circuit Or Battery Connections Have A Defect:

Inspect all cables and connections. Clean and tighten all connections. Make replacement of defective parts.

3. Brushes Have A Defect:

Install new brushes.

4. Rotor (Field Coil) Has A Defect:

Install a new rotor.

Problem 26: Alternator Charge Rate Is Low Or Not Regular

Probable Cause:

1. Loose Drive Belt For Alternator:

Make an adjustment to put the correct tension on the drive belt.

2. Charging Or Ground Return Circuit Or Battery Connections Have A Defect:

Inspect all cables and connections. Clean and tighten all connections. Make replacement of defective parts.

3. Alternator Regulator Has A Defect:

Make an adjustment or replacement of alternator regulator.

4. Alternator Brushes Have A Defect:

Install new brushes.

5. Rectifier Diodes Have A Defect:

Make replacement of rectifier diode that has a defect.

6. Rotor (Field Coil) Has A Defect:

Install a new rotor.

Problem 27: Alternator Charge Too High

Probable Cause:

1. Alternator Or Alternator Regulator Has Loose Connections:

Tighten all connections to alternator or alternator regulator.

2. Alternator Regulator Has A Defect:

Make an adjustment or replacement of alternator regulator.

Problem 28: Alternator Has Noise

Probable Cause:

1. Drive Belt For Alternator Is Worn Or Has A Defect:

Install a new drive belt for the alternator.

2. Loose Alternator Drive Pulley:

Check key groove in pulley for wear. If groove is worn, install a new pulley. Tighten pulley nut according to Specifications.

3. Drive Belt And Drive Pulley For Alternator Are Not In Alignment:

Make an adjustment to put drive belt and drive pulley in correct alignment.

4. Worn Alternator Bearings:

Install new bearings in the alternator.

Problem 29: Short Spark Plug Life

Probable Cause:

1. Wrong Polarity Of Connections At Transformers:

Check wiring diagrams in Systems Operation. Make change to the connection of wires to the primary coil of transformers.

2. Wrong Magneto Timing (Ignition Sequence):

Time magneto to engine.

3. Wrong Spark Plugs:

Install correct spark plugs.

Problem 30: Pre-Ignition

Probable Cause:

1. Worn Spark Plugs:

Clean and make adjustment to the plug gap. If worn install new plugs.

2. Water Leakage In Cylinder Or Combustion Gas In Coolant:

Inspect spark plug adapter gasket. Check spotface for adapter in head for roughness. Install a new adapter to correct torque with the engine COLD.

Problem 31: Detonation

Probable Cause:

1. Wrong Magneto Timing:

Make adjustment to magneto timing.

2. Deposits in Combustion Chamber:

Remove deposits from combustion chambers.

3. High Ambient Air Temperature:

Check for high engine room temperature or high temperature of water to aftercooler.

4. Overload:

Reduce the load.

5. Obstructions In Aftercooler:

Inspect, clean or install new aftercooler as necessary.

Problem 32: Gas Supply Line Shutoff Valve Failure

Probable Cause:

1. Defect In Solenoid:

Install new solenoid.

2. Wrong Electrical Rated Solenoid:

Install new solenoid with correct electrical rating.

3. Defect In Wiring And/Or Connection:

Correct the defect in wiring and connections.

Problem 33: Instrument Panel Gauge Switches Do Not Stop Engine

Probable Cause:

1. Loose Connection Or Defect In Wiring:

Check the wiring and tighten the connections at overspeed shutoff, water temperature gauge, oil pressure gauge, magnetic switch, stop switch, valve solenoid in gas supply line and magneto.

2. Defect In Magneto Switch:

Install a new magneto switch.

3. Defect In Gauge Switches Or Overspeed Shutoff:

Make adjustment to or install new gauge or overspeed shutoff.

4. Defect In Valve Solenoid In The Gas Supply Line:

Install a new solenoid valve.

Problem 34: Instrument Panel Gauge Switches Prevent Engine Start

Probable Cause:

1. Defective Wiring:

Check for wiring contact to ground.

2. Magnetic Switch Failure:

Check wiring in panel for ground and gauge switches for failure.

3. High Water Temperature Or Oil Pressure Gauge Switches Not Reset Or Failure Of Switches:

Permit engine to cool. Engage switches. Make adjustment or install new switches.

Problem 35: Failure Of Overspeed Contactor Switch To Shutoff Engine

Probable Cause:

1. Wrong Electrical Connections:

Check connection, wiring and correct where necessary.

2. Wrong Adjustment:

Make adjustment or install new contactor switch.

Problem 36: Overspeed Contactor Stops Engine At Low Speed

Probable Cause:

1. Wrong Adjustment:

Make adjustment or install new contactor switch if necessary.

Problem 37: Solid State Magneto (Altronic)

1A. Missing On One Or More Cylinders:

1. Use a 1P1790 Firing Indicator to find which cylinder(s) is missing.

NOTE: The brightness of the neon bulb used in this tool indicates the required voltage of the spark plug only. It does not reflect the output of the magneto.

2. Find which wire, in the primary magneto harness, (wire from magneto to transformer), is connected to the problem cylinder. See Wiring Diagrams in Systems Operation.

3. Stop the engine and disconnect the magneto harness connector from the magneto.

NOTE: All ohmmeters must be "zeroed" (adjusted to read zero when the leads are connected together) before using. Follow instructions with your meter.

All meters have a percentage of error because of the type of meter movement used. This error can be from 3 to 5%. A variation between meters is normal.

4. Using an ohmmeter having a scale of RX1, connect the probes between the pin of the problem cylinder, (pin in wiring harness), and a good ground. Read the resistance. The resistance should be between .1 and .2 ohms. If reading is within specification the primary circuit is not defective. Proceed to Step 7.

A reading of less than .1 ohm indicates grounded primary wire or shorted primary in the transformer. A reading of more than .2 ohms indicates poor connections, defective primary in transformer, or poor ground connection.

5. To locate the defect, disconnect the primary wire from the transformer, (wire from magneto). Connect the ohmmeter to the primary stud of the transformer and ground. Check resistance again. Correct reading is .1 to .2 ohms.

Correct reading: defect in primary harness wire or connector in harness.

Incorrect reading: defective transformer or poor ground.

6. Connect the ohmmeter across the primary terminals of the transformer. Read the resistance. Correct reading is .1 to .2 ohms.

Correct reading: poor ground.

Incorrect reading: defective transformer.

7. With the magneto harness still disconnected, remove the spark plug high tension lead from the spark plug. Do not remove the transformer.

8. Using a scale of RX100 or RX1000, connect the ohmmeter between the spark plug connector and ground. The resistance should be 5,000 to 8,000 ohms.

Correct reading: defective spark plug or magneto.

Incorrect reading: defective spark plug high tension lead, transformer or ground.

9. Remove the spark plug high tension lead from the transformer. Read resistance between high tension outlet of the transformer to ground. The resistance should be 5,000 to 8,000 ohms.

Correct reading: defective spark plug high tension lead and/or connections.

Incorrect reading: defective transformer or ground.

10. Connect ohmmeter between the high tension outlet of the transformer and ground terminal of the transformer. The correct reading is 5,000 to 8,000 ohms.

Correct reading: defective ground.

Incorrect reading: defective transformer.

1B. Engine Dead And Has No Spark:

1. Disconnect the M₁ terminal of the magnetic switch on the engine instrument panel. Try to start the engine.

Engine Starts: Defect in shutdown circuit. Repair as required.

Engine Does Not Start: Proceed To Step 2.

2. Connect an ohmmeter between the wire that was removed from the magnetic switch M₁ terminal and ground.

An ohmmeter reading of infinite (500,000 ohms or greater).

a. The wire is not grounded.

b. Possible defective magneto.

A resistance indication on the ohmmeter.

a. Grounded wire between instrument panel and magneto.

b. Defective magneto.

3. Remove the wiring harness connector from the magneto. Connect an ohmmeter between the G pin in the wiring harness connector and ground.

a. Any resistance indication means that the wire is grounded. Replace or repair as required.

b. A reading of infinite indicates that the wire is not grounded. Defective magneto. Repair or replace the magneto.

Show/hide table

NOTICE
Be sure to reconnect the wire to the magnetic switch and the connector to the magneto after the repairs are made.

Ignition System

Magneto

Make a test of the magneto on the engine in the same way as any other magneto: Check the condition (intensity) of the spark at the spark plug. When testing, remember that the condition of the instrument panel components; magnetic switch, stop switch, oil pressure gauge and water temperature gauge have an effect on the magneto output. A defect in, or an activated overspeed shutoff contactor, and/or gas line solenoid valve can cause an indication of a defect in the magneto.

2P2340 Magneto Test Bench

A test of the Fairbanks Morse magneto can be used to find a defect in electrical components. The 2P2340 Magneto Test Bench must be used to make the tests.

The Special Instruction Form No. GEG02059 comes with the test bench, and gives the test procedure. A disassembly of the magneto is needed to test the components. Make reference to SCSA Solid State Magneto, Form No. REG01103 for component test and replacement procedure.

To test the Altronic magneto refer to the Troubleshooting section, Solid State Magneto, Altronic.

Timing Of Magneto To Engine (Fairbanks Morse)

Magnetos on SAE Opposite Rotation (clockwise) engines turn in the same direction as those on SAE Standard Rotation (counterclockwise) engines.

Magnetos are available in either clockwise or counterclockwise rotation. These engines need a counterclockwise rotation magneto (CCW) as seen from the drive end. "CCW" is on the magneto name plate for identification of its correct rotation.

1. Remove the cover for timing pointer from the right side of the flywheel housing.

2. Turn crankshaft in direction of engine rotation until desired piston is coming up on compression stroke. See Top Center Timing Chart to find the correct flywheel marking.

5P7307 Engine Turning Tool

3. Stop turning when desired timing mark is directly under flywheel pointer. See chart of Timing Advance for various conditions such as gas used and compression ratio.

NOTE: After-top-center (ATC) timing, with engine stopped, is needed under some conditions. When flywheels with no ATC marks are found, put a mark on the outside diameter of the flywheel by using the same dimensions from the existing marks on the flywheel.

4. With magneto off the engine, remove timing bolt (8) and turn magneto drive until yellow mark (drilled hole) on pulser gear is in center of opening.

Cylinder Numbering System
(A) Flywheel end. (B) Left side. (C) Right side.

Flywheel Timing Marks (Seen From Right Side Of Engine)
(1) Flywheel pointer. For G399 Engine right side (upper) magneto.

Flywheel Timing Marks (Seen From Right Side Of Engine)
(1) Flywheel pointer. For G379 and G398 Engines.

Flywheel And Magneto Timing Marks
(2) SAE Standard [(CCW) counterclockwise] rotation G398 and G379 Engines. (3) SAE Opposite [(CW) clockwise] rotation G398 Engine. (4) SAE Opposite [(CW) clockwise] rotation G379 Engine.

Flywheel And Magneto Timing Marks
(5) SAE Standard [(CCW) counterclockwise] rotation G399 Engines right side and left side. NOTE: At point (5) the flywheel has a mark "6-12 CW". Use this 30° line for top center for left side number 12 cylinder, on SAE Opposite rotation engines. (6) Top center mark for "1-15", either rotation, also is 30° BTC for SAE Opposite [(CW) clockwise] rotation G399 Engine left side number 12 cylinder. (7) SAE Opposite [(CW) clockwise] rotation G399 Engine right side.

Magneto Timing Bolt
(8) Timing bolt.

NOTE: Flywheel marks shown are only an illustration of the before-top-center side of TC (top center) on the flywheel. For exact timing degrees, see chart of Advance Timing.

Drive Tang And Drive Slot Positions (Viewed from the rear of the engine)
(9) Drive tangs and drive slots. (A) G399 Engine magnetos. (B) G379 Engine magnetos. (C) G398 Engine magnetos.

5. Put the tangs and drive slots (9) of the magneto in correct position for timing. The drive coupling can be pulled out, then turned and pushed in to engage the gear teeth to correct the position.

6. Install the magneto. The drive tang and slot will engage.

7. To make a last timing adjustment, turn the magneto at the drive housing. Use of a timing light when the engine is running at rated speed. Fasten timing light to plug terminal for cylinder shown in Top Center Timing Chart.

Timing Of Magneto To Engine (Solid State Altronic)

Magnetos on SAE Opposite Rotation (clockwise) engines turn in the same direction as those on SAE Standard Rotation (counterclockwise) engines.

Magnetos are available in either clockwise or counterclockwise rotation. These engines need a counterclockwise rotation magneto (CCW) as seen from the drive end. "CCW" is on the magneto name plate for identification of its correct rotation.

1. Remove the cover for timing pointer from the right side of the flywheel housing.

2. Turn crankshaft in direction of engine rotation until desired piston is coming up on compression stroke. See Top Center Timing Chart to find the correct flywheel marking.

5P7307 Engine Turning Tool

3. Stop turning when the desired timing mark is directly under flywheel pointer. See chart of Timing Advance for various conditions such as gas used and compression ratio.

4. The magneto timing marks (1) must be in alignment when the No. 1 piston is at the correct BTC position.

Magneto Timing Marks
(1) Timing marks.

5. If not correct, remove the magneto from the engine.

Magneto Drive Tang
(2) Drive tang.

6. Put timing marks (1) in the correct position with drive tang (2) positioned as shown.

7. Position the magneto drive slots in proper position for timing. The drive coupling can be pulled out, then positioned and pushed in for engagement.

8. Install the magneto. The drive tang and slot will engage.

9. Make final timing adjustment by rotating the magneto at the drive housing mounting and with the use of a timing light when the engine is running at rated speed.

Spark Plugs And Adapters

If the spark plug adapter does not have a covered seat, water leakage or detonation and preignition can be the result. Adapters are installed and removed with an 8S7227 Wrench and 8H8538 Socket.

Voltage to cause the spark will change with the spark plug condition and engine load. A new spark plug in an engine at low idle will take 3,000 to 6,000 volts. At full load, this voltage will be 8,000 to 10,000 volts. When the gap of the spark plug needs adjustment the voltage needed will be over 10,000 volts. Voltage needed will go higher if plug gap adjustment is not made. Spark plugs start to cause the engine to run rough (fire erratically) when the spark plug voltage needs go higher than 10,000 volts.

Plug gap must be kept at 0.36 ± 0.03 mm (.014 ± .001 in.). The use of 1P1790 Firing Indicator is an aid for finding ignition problems. Follow the instructions that come with the tool.

Put liquid soap on the seat groove of adapter (1) and seal. Install the adapter into cylinder head and tighten to a torque of 205 ± 14 N·m (150 ± 10 lb ft). Spark plugs (3) must be installed to a torque of 35 ± 5 N·m (26 ± 4 lb ft) with 1P7424 Spark Plug Socket (4).

Spark Plug Installation
(1) Adapter. (2) 3/8 in. Drive extension. (3) Spark plug. (4) 1P7424 Spark Plug Socket.

Adjustment Of Gauge Contact Point

The adjustment of the contact for the pressure gauge for oil is correct when the engine is stopped at 55 kPa (8 psi) oil pressure. The correct adjustment of the gauge for water temperature is when the engine is stopped at 99°C (210°F).

Adjustment of the gauges is made with a small hollow head screw wrench.

Water Temperature Gauge
(1) Adjustment screw.

Oil Pressure Gauge
(2) Adjustment screw.

Wiring Diagrams For The Magneto

The two diagrams here are for the G379, G398 and G399 Engines. Only two diagrams are needed because the early G399 Engine uses two 8 cylinder magnetos.

12 Cylinder Air - Gap Schematic 12 Cylinder Magneto Diagram
(1) Pulser coil. (2) Terminal strip (upper on power board). (3) Distribution board. (4) Terminal strip (upper on distribution board). (5) Terminal strip (lower on power board). (6) Power board. (7) Terminal strip (lower on distribution board). (8) Plug connector. (9) Generator coil. (10) Capacitor. (11) Terminal strip (on auxiliary distribution board). (12) End cover. (13) Auxiliary distribution board.

8 and 16 Cylinder Air - Gap Schematic 8 and 16 Cylinder Magneto Diagram
(1) Pulser coil. (2) Terminal strip (upper on power board). (3) Distribution board. (4) Terminal strip (upper on distribution board). (5) Terminal strip (lower on power board). (6) Power board. (7) Terminal strip (lower on distribution board). (8) Plug connector. (9) Generator coil. (10) Capacitor. (11) End cover.

Camshaft Cluster Gear Installation

1. Install the small cluster gear (2), the thrust washer and the retainer and tighten to torque of 80 to 95 N·m (60 to 70 lb ft).

NOTE: Make sure the No. 1 piston is at top center on the compression stroke.

2. Mark the cluster gear C-mark and the crankshaft gear punch marked tooth with chalk. The back of the gears can be marked for checking with a mirror after installation.

Installing Cluster Gear
(1) Large cluster gear. (2) Small cluster gear. (3) Retainer. (4) A-marks. (5) Dowel. (6) Alignment mark for flywheel installation. (7) Hole in crankshaft flange.

3. Install large cluster gear (1) so the C-mark on the cluster gear is in alignment with the punch marks on the tooth of the crankshaft gear. Do this by looking through hole (7) in the crankshaft flange.

Checking Alignment With Mirror And Chalk On Back Of Gears

4. On 8 cylinder engines, tilt the large cluster gear and turn the balancer gear until the A-marks (4) are in alignment.

5. With the timing marks in alignment, slide the large cluster gear over the dowel (5) in the small cluster gear and install the mounting bolts.

Timing Balancer Gear In Accessory Drive (G379 Only)

NOTE: The gears of the accessory drive for 12 and 16 cylinder engines do not need to be timed.

V-8 Engines With Standard Rotation

Install the main idler gear with the "C" mark in alignment with the tooth of the crankshaft gear that has four, five or six punch marks. Also, the "B" mark on the main idler gear must be in alignment with the "B" mark on the balancer gear.

SAE Standard Rotation 8 Cylinder Engine

V-8 Engines With Opposite Rotation

Install the idler gear with one of the "R" marks in alignment between two teeth on the crankshaft gear that have two punch marks on each tooth.

The other "R" mark on the idler gear must be in alignment with "R" mark on the balancer gear.

SAE Opposite Rotation 8 Cylinder Engine

Gas, Air Inlet And Exhaust System

Restriction Of Air Inlet And Exhaust

There will be a reduction of horsepower and efficiency of the engine if there is a restriction of the air inlet or exhaust system.

Air flow through the air cleaner must not have a restriction of more than 381 mm (15 in.) of water difference in pressure.

Back pressure from the exhaust (pressure difference measurement between exhaust outlet elbow and atmosphere) must not be more than 864 mm (34 in.) for naturally aspirated and 686 mm (27 in.) for turbocharged engines measured between the turbocharger outlet and atmosphere.

Performance Evaluation Turbocharged Engines

When an engine has no power, it is desirable to make a quick check with instruments to find the approximate horsepower.

Use the 1U5470 Engine Pressure Group to check the pressure in the inlet manifold.

1U5470 Engine Pressure Group

This tool group has a gauge to read pressure in the inlet manifold. Special Instruction Form No. SEHS8524 is with the tool group and gives information on the use of the group.

Correct engine operating adjustments must be made to get correct results from the instruments and test.

By checking pressure of the inlet manifold and comparison of that pressure with the Fuel Setting Information, correct analysis can be made of engine operating efficiency. This test can be used if engine horsepower is too low, but with no other condition of engine problem.

Gas engines can burn a wide range of gaseous fuels. BTU content of fuel is a measure of the power content of the fuel. The higher BTU content fuels need less gas pressure to get a specific horsepower. The fuel ignition is without the aid of the spark if the compression is too high.

Low octane fuels burn so fast that the timing must be set back. With early timing and low octane fuel, the fast burning fuel burns too much before the piston goes over top center. The result of this is "knocking".

The fuel-air ratio adjustment is made by changing the gas pressure. Too much gas makes a "rich mixture" and not enough gas makes a "lean mixture." Either causes a loss of power. When Propane gas is used, the adjustment of the fuel-air ratio is more difficult to make than when natural gas is used.

The BTU HHV (high heat value) of gaseous fuels is the unit of measurement of fuel heat content. The BTU LHV (low heat value) content is more important. The combustion procedure forms carbon dioxide and water, but, the heat needed for conversion of water into vapor is lost to the engine. The heat that can be used in the fuel is the LHV of the fuel. As a rule, the LHV is 10% less than the HHV on natural gas. When BTU HHV is given, remember to change the specification to BTU LHV so the result is correct.

Measurement Of Exhaust Temperatures

6V5000 Infrared Thermometer Group

Use the 6V5000 Infrared Thermometer Group to check exhaust temperature. Special Instruction Form No. SMHS8149 is with the tool group and gives instructions for the test procedures.

Checking Aftercooler Operation

8T470 Thermistor Thermometer Group

Use the 8T470 Thermistor Thermometer Group to check the operation of the aftercooler.

Special Instruction Form No. SEHS8446 gives the procedures for using the 8T470 Thermistor Thermometer Group.

Turbocharger

Every 7200 hours or if any unusual sound or vibration in the turbocharger is noticed, a quick check of bearing condition can be made without disassembling the turbocharger. This can be done by removing the piping from the turbocharger and by removing the compressor impeller, turbine wheel and compressor cover. Rotate the compressor and turbine wheel assembly by hand and observe by feeling excess end play and radial clearance. The rotating assembly should rotate freely with no rubbing or binding. If there is any indication of the impeller rubbing the compressor cover or the turbine wheel rubbing the turbine housing, recondition the turbocharger or replace with a new or rebuild one.

End clearance is best checked with a dial indicator. Attach a dial indicator with the indicator point on the end of the shaft. Move the shaft from end to end making note of the total indicator reading.

End play for 4MD Turbochargers should be 0.10 to 0.15 mm (.004 to .006 in.). If end play is more than the maximum end play rebuild or replace the turbocharger. End play less than the minimum end play could indicate carbon build up on the turbine wheel and should be disassembled for cleaning and inspection.

Checking Turbocharger Rotating Assembly End Play (Typical Example)

A more reliable check of bearing condition can be made only when the turbocharger is disassembled and the bearings, shaft journal and housing bore diameters can actually be measured.

Checking Turbocharger Radial Clearance (Typical Example)

Radial clearance can also be checked with a dial indicator. Remove the oil return line from the turbocharger. Attach a dial indicator with an extension indicator point long enough to contact the shaft through the oil return hole. Make sure the contact point is centered on the shaft (highest indicator reading). Raise both ends of the shaft all the way then push down in the opposite direction. Total movement of the indicator should be between 0.10 mm (.004 in.) and 0.23 mm (.009 in.). If radial clearance exceeds 0.23 mm (.009 in.) or minimum clearance is under 0.10 mm (.004 in.), the turbocharger should be disassembled and the bearing checked.

NOTE: Care must be taken not to cock the shaft or a false reading will be obtained.

Crankcase (Crankshaft Compartment) Pressure

Broken or damaged pistons or piston rings can be the cause of too much pressure in the crankcase. This condition will cause the engine to run rough. There will also be more than the normal amount of fumes coming from the crankcase breather. This crankcase pressure can also cause the element for the crankcase breather to have a restriction in a very short time. It can also be the cause of oil leakage at gaskets and seals that would not normally have leakage.

Compression

An engine that runs rough can have a leak at the valves, or have valves that need adjustment. Use the test that follows for a fast and easy method to find a cylinder that has low compression, or does not have good fuel for combustion. Find the speed that the engine runs the roughest, and keep it there until the test is finished. Remove the spark plug wires from the spark plugs one at a time. This will stop the flow of current to that cylinder. Do this for each cylinder until a removed wire is found that makes no difference in engine rough running. Be sure to install the wire for the spark plug after each cylinder test before the next wire is removed. This test can also be an indication that the spark plug is bad, so more checking of the cylinder will be needed.

Condition of the valves, valve seats, pistons, piston rings and cylinder liners can be tested by putting air pressure in the cylinder. Special Instruction Form No. GMG00694 gives instructions for the test procedure. It also gives the list of parts needed from Parts Department to make the test.

This test is a fast method of finding the cause of compression loss in a cylinder. Removal of the head and inspection of the valves and valve seats is necessary to find those small defects that do not normally cause a problem. Repair of these problems is normally done when reconditioning the engine.

Cylinder Head

Use a 8S7227 Wrench and 8H8538 Socket to remove and install the spark plug adapters. Put liquid soap on the bore in head and seal. Put 5P3931 Anti-Seize Compound on the threads.

Valves

The illustration shows the 5S1330 Valve Spring Compressor Assembly with the 5S1329 Jaw (1) to put the valve spring under compression. When installing the valve keepers, use the 5S1322 Valve Keeper Installer (2) with the compressor assembly.

Compressing Valve Springs
(1) 5S1329 Jaw. (2) 5S1322 Valve Keeper Installer.

Valve Seat Inserts

Tools needed to remove and install seat inserts are in the 6V4805 Valve Insert Puller Group. Special Instruction Form No. SMHS7935 gives an explanation for this procedure. For easier installation, lower the temperature of the insert before it is installed in the head.

Valve Guides

5P3536 Valve Guide Gauge Group

The intake and exhaust valves operate in replacement type valve guides. After the valves have been removed, clean the valve stems and valve guides. Use the 5P3536 Valve Guide Gauge Group to check the valve guides for wear. Instructions are in Special Instruction Form No. GMG02562.

The 4H446 Driver and 5P1726 Bushing is used for installation of new valve guides.

Procedure For Measuring Camshaft Lobes

To find lobe lift, use the procedure that follows:

A. Measure camshaft lobe height (B) of one exhaust and one intake lobe.

B. Measure base circle (C) of the same exhaust and intake lobes.

C. Subtract base circle (STEP B) from lobe height (STEP A). The difference is actual lobe lift (A).

D. Specified camshaft lobe lift (A) is 10.236 mm (.4030 in.).

Maximum permissible difference between actual lobe lift (STEP C) and specified lobe lift (STEP D) is 0.64 mm (.025 in.).

Camshaft Lobe
(A) Lobe lift. (B) Lobe height. (C) Base circle.

Locating Top Center Compression Position For No. 1 Piston

5P7307 Engine Turning Tool
(2) 5P7306 Housing. (3) 5P7305 Gear.

No. 1 piston at top center on the compression stroke is the starting point for all timing procedures.

NOTE: The engine is seen from the flywheel end when the direction of crankshaft rotation is given. Normal direction of crankshaft rotation for standard engines is counterclockwise, and for opposite rotation engines is clockwise.

1. Remove the valve cover for No. 1 cylinder. The two valves at the front of the right bank are the intake and exhaust valves for No. 1 cylinder.

2. Remove the timing mark cover from the right side of the flywheel housing.

Timing Marks On Flywheel (16 Cylinder Engine Illustrated)
(1) Pointer.

3. Remove the starter from the right side of the engine. Install 5P7307 Engine Turning Tool.

NOTE: Put 5P960 Grease in bore of 5P7306 Housing before the pinion is installed.

Timing Marks On Flywheel (8 and 12 Cylinder Engines Illustrated)
(1) Pointer.

4. Turn the crankshaft in a direction opposite of normal rotation approximately 30 degrees. The reason for making this step is to be sure the play is removed from the timing gears when the engine is put on top center.

5. Turn the crankshaft in the direction of normal rotation until the timing marks on the flywheel are in alignment with the pointer in the flywheel housing.

NOTE: If the crankshaft is turned beyond the timing mark, turn the crankshaft in the direction opposite of normal rotation a minimum of 30 degrees before the crankshaft is turned to the timing mark again.

6. The intake and exhaust valves for No. 1 cylinder will be closed if No. 1 piston is on the compression stroke. You can move the rocker arms up and down with your hand. If the No. 1 piston is not on the compression stroke, turn the crankshaft in the direction of normal rotation 360 degrees and make alignment of the timing mark and the pointer.

Valve Clearance

Valve lash (clearance) is checked and adjusted with the engine stopped.

NOTE: When the valve lash (clearance) is checked, adjustment is NOT NECESSARY if the measurement is in the range given in the chart for Valve Clearance Check: Engine Stopped. If the measurement is outside this range, adjustment is necessary. See the chart for Valve Clearance Setting: Engine Stopped, and make the setting to the normal (desired) specifications in this chart.

Valve Clearance Check: Engine Stopped

Exhaust ... 0.81 to 0.97 mm (.032 to .038 in.)

Intake ... 0.30 to 0.46 mm (.012 to .018 in.)

Valve Clearance Setting: Engine Stopped

Exhaust ... 0.89 mm (.035 in.)

Intake ... 0.38 mm (.015 in.)

To make an adjustment to the valve clearance, loosen the locknut on the adjustment screw. Turn the adjustment screw to get the correct clearance shown in the chart Valve Clearance Setting: Engine Stopped. Hold the adjustment screw and tighten the locknut to 55 ± 7 N·m (40 ± 5 lb ft). Recheck the valve clearance. Valve clearance adjustment can be made by using the procedure that follows:

1. Determine the normal direction of crankshaft rotation. See the decal on the flywheel housing.

2. Put No. 1 piston at top center (TC) on the compression stroke. Make reference to Locating Top Center Compression Position For No. 1 Piston.

Flywheel Rotation Decal

Adjusting Valve Lash

3. With No. 1 piston at top center of the compression stroke, adjust the clearance for the valves shown in the chart No. 1 Piston On Compression Stroke.

4. Turn the crankshaft one revolution in the direction of normal rotation and align the pointer and the TC1 mark on the flywheel. The engine now is at top center exhaust stroke No. 1 piston.

5. With No. 1 piston at top center on the exhaust stroke adjust the clearance for the valves shown in the chart No. 1 Piston On Exhaust Stroke.

Cylinder And Valve Location

Water Directors

There are eight water directors (1) pressed into each cylinder head to direct the flow of coolant. On the exhaust side, coolant is directed toward the spark plug adapters and the exhaust valve ports and on the inlet side, toward the other side of the valve ports, as indicated by the V-marks.

Water Directors
(1) Water director. (2) Ferrule. (3) Seal.

Water directors are pressed into place in the heads after aligning the notch on the director with the V-mark on the head.

Replacement type seals (3) and ferrule (2) go between the head and top of the block. Put soap on the inner surface of the seal and place the groove in the seal over the ridge on the ferrule before installing. Use the FT117 Seal and Ferrule Assembly Tool to install the seal on the ferrule.

FT117 Seal And Ferrule Assembly Tool
(4) 5H3182 Pin. (5) 2A3672 Spring. (6) Flat washer. (7) Chain. (8) Upper rod. (9) Connecting pin. (10) Bracket. (11) Connecting joint. (12) Lower rod. (13) Base. (A) Rubber seals. (B) Ferrule.

Differential Pressure Regulator

Regulator
(1) Measurements for testing regulator. (2) Pressure sensing port connection. (3) Spacers. (4) Bypass valve. (5) Breather location. (6) Bypass passage. (7) Exhaust regulator bypass housing. (8) Diaphragm. (9) Shims.

The regulator has two 6.4 mm (.25 in.) spacers (3) for altitude adjustment. Both spacers must be used for operation up to 457 m (1500 feet) altitude. Remove one for operating between 457 and 1219 m (1500 and 4000 feet). All shims can be removed for operating between 1219 and 1981 m (4000 and 6500 feet). Make a small adjustment by adding or removing shims (9). The bolts of the regulator assembly must be sealed.

To test the regulator with both spacers (3) in place, and atmospheric pressure in spring compartment, use a pressure of 47 to 51 kPa (6.65 to 7.20 psi) in the chamber, through connection (2). Measurement at (1) must be 73.5 mm (2.893 in.). Special Instruction Form No. FE034610 shows the equipment for testing and adjusting this regulator.

Use large enough lines to supply the volume of air needed. Use a Tee in the line to connect the gauge. The Tee must be installed so the gauge is at the opposite end of the Tee from the connection to the regulator. The supply pressure will be attached to side of the Tee.

Line Pressure Regulator

Regulate (make adjustment to) pressure in the main gas supply line for the engines. Naturally aspirated engines need main gas supply line pressure of 20 to 140 kPa (3 to 20 psi). Turbocharged engines need more pressure, 85 to 140 kPa (12 to 20 psi). 140 kPa (20 psi) is the maximum pressure which is easily lowered to a usable pressure. If the main gas supply line pressure is above 140 kPa (20 psi), the addition of another regulator is needed.

1. Adjustment of the pressure regulator can be checked while the engine is running, with a water manometer.

Checking Line Pressure Regulator Adjustment
(A) Positive pressure differential. (1) Tee and manometer connection. (2) Adjustment screw. (3) Gas supply at carburetor. (4) Water manometer. (5). Valve.

2. Fasten one end of a water manometer (4) to the gas supply at carburetor (3). On engines with balance line, connect the other end of the manometer to a tee (1) installed at balance line connection at pressure regulator, or to the air inlet to the carburetor to measure the pressure differential (A). On engines with no balance line, connect the manometer only at (3). Let the other end be open to the atmosphere.

NOTE: Valve (5) must be closed before the engine is stopped. This will prevent the manometer fluid from getting into the inlet of the carburetor (3).

3. Remove the cap and turn screw (2) until the pressure differential (A) is in the permissible range.

NOTE: On turbocharged engines a special tool is needed to prevent leakage of boost pressure when the regulator cap is removed.

The permissible range of value (A) is as follows:

Natural Gas at 1000 BTU (low heat value) measurement (A): Permissible range is 127 mm H₂O (5 in. H₂O). Vaporous Propane gas at 2500 BTU (low heat value) measurement (A): Make an adjustment to the gas line pressure regulator (12) to get a differential pressure of 254 mm H₂O (10 in. H₂O) of gas to the Thermac pressure reducing valve (7). The Thermac valve will give a reduction to a negative differential pressure of -25.4 mm H₂O (-1 in. H₂O). The load adjusting valve (10) in the gas line before the carburetor (9) must have an adjustment made so the negative differential pressure is -50.8 mm H₂O (-2 in. H₂O).

Regulator Adjustment Tool

Propane Gas Regulation Components
(6) Balance line. (7) Thermac reducing valve. (8) Air inlet. (9) Carburetor. (10) Load adjusting valve. (11) Fuel inlet line. (12) Line pressure regulator. (13) Air fuel mixture. (14) Propane gas supply.

Any other gas used with different specifications will need more or less differential pressure settings. This is because of the BTU low heat value of gas. Special information must be ordered from the Service Department of Caterpillar Inc.

Carburetor

The carburetor and governor linkage adjustment is given in the subject Governor.

Turn the power mixture adjustment to center between "R" (rich) and "L" (lean). Make fuel mixture adjustments by changing the gas pressure from the line pressure regulator.

Turn idle adjustment screw (1) four full turns open (from the closed position).

Carburetor Adjustments
(1) Idle adjustment screw. (2) Throttle stop screw.

Turn throttle stop screw (2), to obtain desired idle speed. See Fuel Setting Information for low idle rpm.

Balance Adjustment Of The Throttle Valve (Synchronization)

If the throttle valves do not open at the same time or amount on both carburetors, the load will be out of balance between the left and right cylinders. The result will be rough operation.

Adjustment (Engine Not Operating)

1. Disconnect governor linkage at each throttle shaft lever (2).

2. Turn the screw (1) out until each throttle will close before the screw makes contact with the stop. Slot (3) in the end of the throttle shaft shows the position of the throttle plate.

3. Turn each stop screw (1) so it will just make contact with the stop while the throttle plate is closed. The lever (2) must be installed on the throttle shaft, in the same angle relation to slot (3) for both carburetors.

Throttle Valve Synchronization
(1) Throttle stop screw for low idle. (2) Throttle shaft lever. (3) Slot.

4. Move the control lever for the governor to the OFF position.

5. Make adjustments to the length of the linkage between governor and carburetor until both connections can be made while the throttle plates are completely closed, and the governor weights fully closed.

6. Connect both linkages to throttle shaft levers (2).

7. Set both throttle stop screws (1) for low idle rpm.

Adjustment (Engine Operating)

Check that each regulator is holding the correct pressure for the fuel being used. Also, check that there is the same pressures to both carburetors.

Connect one differential pressure gauge in the 1U5470 Engine Pressure Group to the plug opening in the inlet manifold. Connect the other gauge to the similar connection on the other side of the engine. Special Instruction Form No. SEHS8524 is with the tool group and gives instructions for its use..

1U5470 Engine Pressure Group

With the engine running and governor control lever in low idle position, make adjustment to the length of the rods. Make the engine rpm come up to full load and check gauge indication. Change if necessary. The adjustment is correct when the gauge indication on the two gauges are within 104.14 mm H₂O (4.1 in. H₂O) or 7.62 mm Hg (.3 in. Hg).

NOTE: Do not change the adjustment of the pressure regulator to balance (synchronize) the pressures in the inlet manifolds. To get the balance (synchronization), make adjustments to the linkage only.

Governor Adjustments

The low and high idle rpm settings for this engine are shown in the Fuel Setting Information.

Stop Screw Adjustment

Make adjustment of the stop screw in the stop collar to make the collar travel 15.37 mm (.605 in.).

Tools In Place For Stop Screw Adjustment
(1) 9S225 Bracket. (2) Stop collar. (3) Terminal shaft lever.

Remove the linkage from governor terminal shaft lever (3) and remove governor cover. Fasten 9S225 Bracket (1) with 2H191 Bolt as shown and install 8S2283 Dial Indicator. Measure the maximum movement of stop collar (2) between the position fuel full on to fuel off. To do this, make dial indicator readings when both levers and collar are in the same relation to each other, fuel full on (stop collar on stop) and full off (stop collar raised). Lift the stop collar by hand in the fuel off direction, carefully against the resistance of the wave washer. Make an adjustment to the stop screw to make the travel 15.37 mm (.605 in.) and tighten the locknut to a torque of 12 ± 4 N·m (9 ± 3 lb ft). Check the adjustment.

Adjustment Of Linkage To The Carburetor

1. On earlier engines assemble end levers (2) to cross shaft at angle of 135° from center lever (1) as shown.

NOTE: On later engines and on earlier engines that have interference at assembly, change the 90° angle to 80° from horizontal for a combined angle of 125°.

2. With throttle plates closed, assemble carburetor levers (5) and (7) on carburetor throttle shaft at 45° angles from horizontal as shown.

3. Put center lever (1) in vertical position. Make adjustments to rods (6) and install them with both throttle plates in the CLOSED position.

4. Open the throttle plates to check correct position of levers.

Carburetor Linkage
(1) Center lever. (2) End levers. (3) Governor lever. (4) Rod. (5) Carburetor lever. (6) Rods. (7) Carburetor lever.

5. With governor lever (3) at shutoff position, make adjustments to rod (4) and install it between center lever (1) and governor lever (3). The center lever must be in the vertical position.

6. Make adjustments necessary to the carburetor and gas regulator.

Three basic uses of the 1P2385 Protractor tools are shown here.

1P2385 Protractor Tool Use
(A) Indicator used for angle setting. (B) Protractor plate edge in alignment with lever. (C) Vertical housing face and extension arm are in alignment. (D) Bubble in level. (E) Indicator used for angle setting. (F) Extension arm in alignment with lever. (G) Extension arm in alignment with lever. (H) Plate edge in alignment with second lever. (I) Indicator used for angle setting. (J) Angle between lever and vertical face of housing. (K) Angle between level and lever. (L) Angle between levers.

Adjustment Of Linkage To The Governor

Make the adjustment to the linkage when the engine is running at low idle as in the steps that follow:

Linkage For Governor Control
(1) Lever. (2) Rod. (3) Lever for the control shafts. (4) Length.

1. Make adjustment to rod (2) to get length (4). Length (4) is 266.7 mm (10.5 in.) for G379 and G398 Engines, and 330.2 mm (13.31 in.) for G399 Engines.

2. Fasten the rod to both levers. The clamp bolt for lever (3) for the control shaft must be loose.

3. With the governor at the SHUT OFF position, put lever (1) on the governor shaft at the 33° angle as shown, and hold it there.

4. Clamp lever (3) on the control shaft.

High Idle Adjustment

6V3121 Multitach Group
(1) Carrying case. (2) Power cable. (3) Tachometer generator. (4) Tachometer drive group. (5) Multitach.

The 6V3121 Multitach Group can measure engine speed from a tachometer drive on the engine. It also has the ability to measure engine speed from visual engine parts in rotation.

Special Instruction From No. SEHS7807 is with the 6V3121 Multitach Group and gives instructions for the test procedure.

Make high idle rpm adjustments by removing the cover (1) at the rear of the governor, and turning the adjustment screw (3). Turning screw in a clockwise direction will give a decrease in the idle rpm. The shape of the retainer hole in the cover (1) prevents the screw from turning, after the adjustment is made.

Governor Adjustments
(1) Cover. (2) Retainer hole. (3) Adjustment for high idle.

After setting the high idle rpm, move the governor control lever to change the engine rpm. Move it back to the idle position and again check the idle rpm. Make this adjustment procedure until the rpm is correct.

Adjustments to the low idle rpm are made at the carburetors.

Lubrication System

One of the problems in the list that follows will generally be an indication of a problem in the lubrication system for the engine.

Too Much Oil Consumption

Oil Pressure Is Low

Oil Pressure Is High

Too Much Bearing Wear

Too Much Oil Consumption

Oil Leakage On Outside Of Engine

Check for leakage at the seals at each end of the crankshaft. Look for leakage at the oil pan gasket and all lubrication system connections. Check to see if oil comes out of the crankcase breather. This can be caused by combustion gas leakage around the pistons. A dirty crankcase breather will cause high pressure in the crankcase, and this will cause gasket and seal leakage.

Oil Leakage Into Combustion Area Of Cylinders

Oil leakage into the combustion area of the cylinders can be the cause of blue smoke. There are four possible ways for oil leakage into the combustion area of the cylinders:

1. Oil leakage between worn valve guides and valve stems.

2. Worn or damaged piston rings, or dirty oil return holes.

3. Compression ring not installed correctly.

4. Oil leakage past the seal rings in the impeller end of the turbocharger shaft.

Too much oil consumption can also be the result if oil with the wrong viscosity is used. Oil with a thin viscosity can be caused by fuel leakage into the crankcase, or by increased engine temperature.

Measuring Engine Oil Pressure

An oil pressure gauge that has a defect can give an indication of low oil pressure.

The 1U5470 Engine Pressure Group can be used to check engine oil pressure.

1U5470 Engine Pressure Group

This tool group has a gauge to read oil pressure in the engine. Special Instruction Form No. SEHS8524 is with the tool group and gives instructions for the test procedure.

This procedure must be followed exactly for the pressure readings to have any value for comparison with Engine Oil Pressure Chart.

1. Be sure that the engine is filled to the correct level with SAE 30 oil. If any other viscosity of oil is used, the information in the Engine Oil Pressure Chart does not apply.

2. Connect the 1U5470 tool group to one of the ports in the back side of the governor or governor drive housing. Remove the pipe plug on the oil outlet elbow on the oil cooler and install a probe from the 8T470 Thermistor Thermometer Group.

3. Start the engine and run to get the oil temperature to 93 ± 6°C (200 ± 10°F).

4. Keep the oil temperature constant with the engine speed at 1200 rpm. Make a comparison of the gauge reading and the chart.

If the results do not fall within the pressure range given in the chart, find the cause and correct it. Engine failure or a reduction in engine life can be the result if engine operation is continued with oil manifold pressure outside this range.

Oil Pressure Is Low

Crankcase Oil Level

Check the level of the oil in the crankcase. Add oil if needed. It is possible for the oil level to be too far below the oil pump supply tube. This will cause the oil pump to not have the ability to supply enough lubrication to the engine components.

Oil Pump Does Not Work Correctly

The inlet screen of the supply tube for the oil pump can have a restriction. This will cause cavitation (low pressure bubbles suddenly made in liquids by mechanical forces) and a loss of oil pressure. Air leakage in the supply side of the oil pump will also cause cavitation and loss of oil pressure. If the bypass valve for the oil pump is held in the open (unseated) position, the lubrication system cannot get to maximum pressure. Oil pump gears that have too much wear will cause a reduction in oil pressure.

Oil Filter And Bypass Valve

As the oil filters become filled with dirt, a reduction of engine oil pressure will be seen until oil filter bypass valve (1) opens. When the bypass valve opens, unfiltered oil will go through the engine.

When the oil pressure on the clean side (inside) of the elements becomes 85 to 105 kPa (12 to 15 psi) less than the oil pressure to the unfiltered side (outside) of the elements, filter condition indicator (2) will move up approximately half way. This shows that the oil filter elements must be changed.

Oil Filter Bypass Valve
(1) Valve.

Filter Condition Indicator
(2) Filter condition indicator.

Too Much Clearance At Engine Bearings Or Open, Broken Or Disconnected Oil Line Or Passage In Lubrication System

Components that are worn and have too much bearing clearance can cause oil pressure to be low. Low oil pressure can also be caused by an oil line or oil passage that is open, broken or disconnected.

Oil Cooler

Look for a restriction in the oil passages of the oil cooler.

If the oil cooler has a restriction the oil temperature will be higher than normal when the engine is running. The oil pressure of the engine may become low if the oil cooler has a restriction.

Oil Pressure Is High

Oil pressure will be high if the pressure regulating valve for the oil pump cannot move from the closed position.

Too Much Bearing Wear

When some components of the engine show bearing wear in a short time, the cause can be a restriction in an oil passage. A broken oil passage can also be the cause.

If the gauge for oil pressure shows the correct oil pressure, but a component is worn because it is not getting enough lubrication, look at the passage for oil supply to that component. A restriction in a supply passage will not let enough lubrication get to a component and this will cause early wear.

Turbocharger Lubrication Valve (G379 And G398 Engines)

When the gauge for oil pressure shows the correct oil pressure and bearing failure or wear is present in both turbochargers, check the operation of the turbocharger lubrication valve. The valve can be open and allow unfiltered oil to constantly lubricate the turbocharger.

Turbocharger Lubrication Valve At Right Rear Of Engine

Prelube System

The components of this system that can be checked are lines, oil pump and check valve. There are two test plugs in the pump housing. Test the pressure with the 1U5470 Engine Pressure Group. The correct pressure is 170 kPa (25 psi) at plug (1) in outlet side of the pump.

If the pump is worn, the low oil pressure and flow may be increased by removing gaskets from between head (2) and housing. End play of the rotor should be 0.08 to 0.13 mm (.003 to .005 in.).

A check of the function of the check valve (3) can be made at test plug (1). After the engine is running and oil pressure is shown on the instrument panel, and the prelube pump motor has stopped, no pressure at the test plug (1) shows the check valve is working correctly.

Test Location Of Prelube Pump
(1) Test plug. (2) Pump head. (3) Check valve.

Cooling System

This engine has a pressure type cooling system. A pressure type cooling system gives two advantages. The first advantage is that the cooling system can have safe operation at a temperature that is higher than the normal boiling (steam) point of water. The second advantage is that this type system prevents cavitation (low pressure bubbles suddenly made in liquids by mechanical forces) in the water pump. With this type system, it is more difficult for an air or steam pocket to be made in the cooling system.

The cause for increased engine temperature is generally because regular inspections of the cooling system were not made. Make visual inspection of the cooling system before a test is made with test equipment.

Visual Inspection Of The Cooling System

Show/hide table

DO NOT loosen the pressure cap on a hot engine. Steam or hot coolant can cause severe burns.

1. After the engine is cool, loosen the filler cap (on radiators with a pressure cap turn it to the first stop) to let pressure out of the cooling system. Then remove filler or pressure cap.

2. Check coolant level in the cooling system.

3. Look for leaks in the system.

4. Look for bent radiator fins. Be sure that air flow through the radiator does not have a restriction.

5. Inspect the drive belts for the fan.

6. Check for damage to the fan blades.

7. Look for air or combustion gas in the cooling system.

8. Inspect the filler cap and the surface that seals the cap. This surface must be clean.

Testing The Cooling System

Remember that temperature and pressure work together. When a diagnosis is made of a cooling system problem, temperature and pressure must both be checked. Cooling system pressure will have an effect on cooling system temperatures. For an example, look at the chart to see the effect of pressure and height above sea level on the boiling (steam) point of water.

Test Tools For Cooling System

The 8T470 Thermistor Thermometer Group is used in the diagnosis of overheating (engine hotter than normal) or overcooling (engine cooler than normal) problems. This group can be used to check temperatures in several different parts of the cooling system. The testing procedure is in Special Instruction Form No. SEHS8446.

8T470 Thermistor Thermometer Group

The 8T2700 Blowby/Air Flow Indicator Group is used to check the air flow through the radiator core. The operating instructions are included in the group.

8T2700 Blowby/Air Flow Indicator Group

The 6V3121 Multitach Group is used to check the fan speed. The testing procedure is in Special Instruction Form No. SEHS7807.

6V3121 Multitach Group

Pressure Cap Test

One cause for a pressure loss in the cooling system can be a bad seal on the pressure cap of the system. Inspect the pressure cap carefully. Look for damage to the seal or to the surface that seals. Any foreign material or deposits on the cap, valve, seal, or surface that seals must be removed.

Show/hide table

DO NOT loosen the pressure cap on a hot engine. Steam or hot coolant can cause severe burns.

Typical Schematic Of Pressure Cap
(A) Sealing surface of cap and radiator.

1. After the engine is cool, loosen the pressure cap to the first stop and let the pressure out of the cooling system. Then remove the pressure cap.

2. Put the pressure cap on the 9S8140 Cooling System Pressurizing Pump Group.

9S8140 Cooling System Pressurizing Pump Group
(A) Release valve. (B) Adapter. (C) Hose.

3. Look at the gauge for the exact pressure that makes the pressure cap open.

4. Make a comparison of the reading on the gauge with the correct pressure at which the pressure cap must open.

NOTE: The correct pressure that makes the pressure cap open is on the pressure cap and is also in the Specifications.

5. If the pressure cap is bad, install a new pressure cap.

Radiator And Cooling System Leak Tests

To test the radiator and cooling system for leaks, use the procedure that follows:

Show/hide table

DO NOT loosen the pressure cap on a hot engine. Steam or hot coolant can cause severe burns.

1. After the engine is cool, loosen the pressure cap to the first stop and let the pressure out of the cooling system. Then remove the pressure cap.

2. Make sure the coolant is over the top of the radiator core.

3. Put the 9S8140 Cooling System Pressurizing Pump Group on the radiator.

9S8140 Pressurizing Pump Group Installed On Radiator That Uses Pressure Cap (Typical Example)

4. Get the pressure reading on the gauge to 20 kPa (3 psi) more than the pressure on the pressure cap.

5. Check the radiator for outside leakage.

6. Check all connections and hoses of the cooling system for outside leakage.

7. If you do not see any outside leakage and the pressure reading on the gauge is still the same after 5 minutes, the radiator and cooling system does not have leakage. If the reading on the gauge goes down and you do not see any outside leakage, there is leakage on the inside of the cooling system. Make repairs as necessary.

Gauge For Water Temperature

NOTE: Make a quick check of water temperature circuit continuity (no opens in the circuit) as follows:

a. Activate the water temperature gauge circuit.

b. Disconnect the wire from the terminal of the water temperature sender.

c. Put the wire in contact with a good ground on the engine for a moment. The pointer of the water temperature gauge must move clockwise.

Show/hide table

NOTICE
Do not ground the water temperature gauge for more than 10 seconds at a time, to prevent damage to the gauge.

If the gauge operates correctly, the problem is with the sender.

Water Temperature Regulators

The completely open temperature for the 6L5851 and 9N2894 Regulators is 92°C (197°F). The completely open temperature for the 9S9160 Regulator is 86°C (187°F).

1. Remove the regulator from the engine.

2. Heat water in a pan to a temperature equal to the completely open temperature of the regulator being tested. Move the water around in the pan to make it all the same temperature.

3. Hang the regulator in the pan of water. The regulator must be below the surface of the water and it must be away from the sides and bottom of the pan.

4. Keep the water at the correct temperature for 10 minutes.

5. After ten minutes, remove the regulator and immediately measure the distance the regulator has opened. The distance must be a minimum of 9.53 mm (.375 in.).

6. If the distance is less than 9.53 mm (.375 in.), make a replacement of the regulator.

Coolant Level Switch

Testing

Lower the coolant level in the system to cause the float (1) to lower and cause the switch points to make contact. This can be done by removing some of the coolant or with application of 70 to 140 kPa (10 to 20 psi) of air pressure to the vent line connection (2) on top of the switch. Look at the float and switch as the coolant level lowers. The float position on the later type switch is shown by the switch operating arm (4). The switch (5) can carry a load of 110V at 3 amperes. The device connected will be activated as the points make contact.

Coolant Level Switch (Earlier Type)
(1) Float. (2) Vent line connection. (3) Terminal Screw.

Adjustment

The terminal screw (3) on the bottom of the earlier switch can be turned in to raise and out to lower the level at which the points will make contact.

Coolant Level Switch (Later Type)
(2) Vent line connection. (4) Switch operating arm. (5) Switch.

V-Belt Tension Chart

Basic Block

Connecting Rods And Pistons

Use the 5H9621 Piston Ring Expander to remove or install piston rings.

Use the 5P3528 Piston Ring Compressor to install pistons into cylinder block.

Tighten the connecting rod bolts in the step sequence that follows:

1. Put Fel-Pro C100 on threads, shank and bolt head seat.

2. Tighten all nuts to 55 ± 5 N·m (40 ± 4 lb ft).

3. Put a mark on each nut and cap.

4. Tighten each nut 120° from the mark.

The connecting rod bearings should fit tightly in the bore in the rod. If bearing joints or backs are worn (fretted), check for bore size as this is an indication of wear because of looseness.

Piston Ring Groove Gauge

A 5P3519 Piston Ring Groove Gauge is available for checking ring grooves with straight sides. For instructions on the use of the gauge, see the Guideline For Reusable Parts; Pistons, Form No. SEBF8049.

5P3519 Piston Ring Groove Gauge

Connecting Rod And Main Bearings

Main bearings are available with 1.27 mm (.050 in.) smaller inside diameter than original size bearings. These bearings are for crankshafts that have been "ground" (made smaller than original size).

Connecting rod bearings are available with 0.64 mm (.025 in.) and 1.27 mm (.050 in.) smaller inside diameter than original size bearings. These bearings are also available with 0.25 mm (.010 in.) larger outside diameter than original size bearings. These bearings are for connecting rods that have been "bored" (made larger than original size).

Cylinder Block

Bore in block for main bearings can be checked with main bearing caps installed without bearings. Tighten the stud nuts to torque shown in the Specifications. Alignment error in the bores must not be more than 0.08 mm (.003 in.).

1P3537 Dial Bore Gauge Group

Special Instruction Form No. SMHS7606 gives the use of 1P4000 Line Boring Tool Group to machine main bearing bores. 1P3537 Dial Bore Gauge Group can be used to check bores. Special Instruction Form No. GMG00981 is with the group.

Cylinder Liner Projection

The correct cylinder liner projection is important to prevent a leak between the liner, cylinder head and block. Use the procedure that follows to check cylinder liner projection.

1. Make sure that the bore and counterbore in the block and the liner flange are clean. Install the cylinder liner without seals in the cylinder block.

Measuring Liner Projection (Earlier)
(1) 3H465 Plate. (2) Dial indicator. (3) 1P2402 Gauge Body. (4) Crossbar. (5) 1P2398 Puller Plate.

Measuring Liner Projection (Later)
(1) 3H465 Plate. (2) Dial indicator. (3) 1P2402 Gauge Body. (4) Crossbar. (5) 1P2398 Puller Plate.

2. Put puller plate (5) on the cylinder liner and put plate (1) in the center of the adapter plate as shown. Install crossbar (4) with nuts, washers, and 3H465 Plates as shown. Tighten the nuts evenly in four steps: 7 N·m (5 lb ft), 20 N·m (15 lb ft), 35 N·m (25 lb ft), and 70 N·m (50 lb ft). The measurement from the bottom of crossbar (4) to the top of cylinder block, must be the same on both sides of the cylinder liners.

3. Install the 1P5512 Contact Point on dial indicator (2). Put the dial indicator in the 1P2402 Gauge Body. To adjust the dial indicator to zero, put dial indicator and gauge body on the back of the 1P5507 Gauge. Move the dial indicator until the hand moves 1/4 turn.

Tighten bolt on body to hold the dial indicator in this position. Turn the dial face until the zero is in alignment with the hand.

4. Measure the cylinder liner projection as close as possible to the four corners of the adapter plate on the liner. The liner projection must be 0.10 to 0.20 mm (.004 to .008 in.). The difference between the four measurements must not be more than 0.05 mm (.002 in.). The maximum difference in height of liners next to each other under the same cylinder head is 0.05 mm (.002 in.).

NOTE: If the liner projection changes from point to point around the liner, turn the liner to a new position in the bore. If the liner projection is still not to specifications, move the liner to a different bore.

5. When the cylinder liner projection is correct, put a temporary mark on the liner and the cylinder block so at final installation the liner can be installed in the correct position.

Cylinder liner projection can be adjusted by the removal of material from (machining) the contact face of the cylinder block with the use of 8S3140 Cylinder Block Counterboring Tool Arrangement. The instructions for the use of the tool group are in Special Instruction Form No. FM055228.

Shims are available for adjustment of the liner projection.

Flywheel And Flywheel Housing

Flywheel Ring Gear

Heat the ring gear to a maximum of 316°C (600°F) to install. Install the ring gear so the chamfer on the gear teeth is next to the starter pinion when the flywheel is installed.

Face Runout (Axial Eccentricity) Of The Flywheel Housing

If any method other than given here is used, always remember bearing clearances must be removed to get correct measurements.

Make tool setup from parts of the 8T5096 Dial Indicator Test Group.

1. Fasten a dial indicator to the crankshaft flange so the indicator anvil will touch the flywheel housing face.

2. Push the crankshaft to the rear to remove all end play before reading the indicator at each point.

Checking Flywheel Housing Face Runout
(A) Bottom. (B) Right side. (C) Top. (D) Left side.

3. With dial indicator set at 0.0 mm (.000 in.) at point (A), rotate crankshaft and take readings at point (B), (C) and (D).

4. The difference between the lowest and highest readings taken at all four points should not exceed 0.30 mm (.012 in.), which is the maximum permissible flywheel housing face runout.

Bore Runout (Radial Eccentricity) Of The Flywheel Housing

8T5096 Dial Indicator Test Group Installed

1. With the dial indicator in position at (C), adjust the dial indicator to "0" (zero). Push the crankshaft up against the top bearing. Write the measurement for bearing clearance on line 1 in column (C).

2. Divide the measurement from Step 1 by 2. Write this number on line 1 in columns (B) & (D).

NOTE: Write the dial indicator measurements with their positive (+) and negative (-) notation (signs). This notation is necessary for making the calculations in the chart correctly.

3. Turn the crankshaft to put the dial indicator at (A). Adjust the dial indicator to "0" (zero).

4. Turn the crankshaft counterclockwise to put the dial indicator at (B). Write the measurement in the chart.

5. Turn the crankshaft counterclockwise to put the dial indicator at (C). Write the measurement in the chart.

Checking Bore Runout Of The Flywheel Housing

6. Turn the crankshaft counterclockwise to put the dial indicator at (D). Write the measurement in the chart.

7. Add lines I & II by columns.

8. Subtract the small number from the larger number in line III in columns (B) & (D). The result is the horizontal "eccentricity" (out of round). Line III, column (C) is the vertical eccentricity.

9. On the graph for total eccentricity find the point of intersection of the lines for vertical eccentricity and horizontal eccentricity.

Graph For Total Eccentricity

10. If the point of intersection is in the range marked "Acceptable" the bore is in alignment. If the point of intersection is in the range marked "Not Acceptable," the flywheel housing must be changed.

Face Runout (Axial Eccentricity) Of The Flywheel

1. Install the dial indicator as shown. Move the flywheel to the front or rear to remove all end play.

Checking Face Runout Of The Flywheel

2. Set the dial indicator to read 0.0 mm (.000 in.).

3. Turn the flywheel and read the indicator every 90°. Be sure to remove end play the same way each time.

4. The difference between the lower and higher measurements taken at all four points must not be more than 0.15 mm (.006 in.), which is the maximum permissible face runout (axial eccentricity) of the flywheel.

Bore Runout (Radial Eccentricity) Of The Flywheel

1. Install the dial indicator (3) and make an adjustment of the universal attachment (4) so it makes contact as shown.

Checking Bore Runout Of The Flywheel
(1) 7H1945 Holding Rod. (2) 7H1645 Holding Rod. (3) 7H1942 Indicator. (4) 7H1940 Universal Attachment.

2. Set the dial indicator to read 0.0 mm (.000 in.).

3. Turn the flywheel and read the indicator every 90°.

4. The difference between the lower and higher measurements taken at all four points must not be more than 0.15 mm (.006 in.), which is the maximum permissible bore runout (radial eccentricity) of the flywheel.

Checking Flywheel Clutch Pilot Bearing Bore

5. Runout (eccentricity) of the bore for the pilot bearing for the flywheel clutch, must not exceed 0.13 mm (.005 in.).

Checking Crankshaft Deflection (Bend)

The crankshaft can be deflected (bent) because the installation of the engine was not correct. If the engine mounting rails are not fastened correctly to the foundation mounting rails, the cylinder block can twist or bend and cause the crankshaft to deflect. This deflection can cause crankshaft and bearing failure.

The crankshaft deflection must be checked after the final installation of the engine. The check must be made with the engine cold and also with the engine at the temperature of normal operation. The procedure that follows can be used to check crankshaft deflection with the engine either cold or warm.

1. Remove an inspection cover from the cylinder block that will give access to the connecting rod journal of the crankshaft nearest to the center of the engine.

Show/hide table

NOTICE
Read the notice on the cylinder block covers before removal of the covers on a warm engine.

2. Turn the crankshaft in the direction of normal rotation until the center of the counterweights just go beyond the connecting rod.

Measuring Deflection Of The Crankshaft
(1) Dial gauge. (2) Mounting face.

3. Install a Starrett Crankshaft Distortion Dial-Gauge No. 696 with Starrett No. 696B Balancer Attachment between the counterweights as shown. Put Dial Gauge (1) within 6.4 mm (.25 in.) of counterweight mounting surface (2). Turn the dial of the indicator to get alignment of the zero and the pointer. Turn the indicator on its end points until the pointer of the indicator will not move from zero.

4. Turn the crankshaft in the direction of normal rotation until the indicator almost makes contact with the connecting rod on the other side of the crankshaft.

NOTE: Do not let the indicator make contact with the connecting rod.

5. The dial indicator reading must not be greater than -0.013 mm (-.0005 in.) close in or +0.025 mm (+.0010 in.) spread for the approximately 300 degrees of crankshaft rotation. Now turn the crankshaft in the opposite direction to the starting position. The dial indicator must now read zero. If the dial indicator does not read zero, do the procedure again.

If the dial indicator reads more than 0.03 mm (.001 in.), the cylinder block is bent. Loosen the bolts that hold the engine mounting rails to the foundation mounting rails and adjust the shims to make the engine straight again. Also check to see if the engine mounting bolts have enough clearance to let the engine have expansion as it gets hot. The only bolts that can have a tight fit are bolts at the right hand rear of the engine and the right hand rear bolt that holds the engine to the oil pan base.

Vibration Damper

Damage to or failure of the damper will increase vibrations and result in damage to the crankshaft. It will cause more gear train noise at variable points in the speed range.

The damper needs replacement when there is a bent, expanded damper case or loose fitting bolt holes. Replacement of the damper is also needed: 1. At major overhaul, 2. At time of crankshaft failure (if a torsional type), 3. When a damper is in defect.

Crankshaft Seals

Crankshaft Seal Thrower And Ring
(1) Rear ring. (2) Rear thrower. (3) Front ring. (4) Front thrower.

Installation Of Crankshaft Seal Thrower
(5) 5B7548 Puller. (6) 7F9540 Hydraulic Puller. (7) 8B7556 Adapter. (8) FT105 Push Plate.

Front Accessory Drive

Accessory Drive Gears
(8 Cylinder Engine Illustrated) (1) Water pump drive gear. (2) Main idler gear. (3) Crankshaft gear. (4) Tube. (5) Thrower. (6), (7) Idler gears. (8) Oil pump drive gear. (9) Balancer gear. (10) Plate.

The gear train of the accessory drive are the same on the 8, 12 and 16 cylinder engines, except for balancer gear (9) used on the 8 cylinder engine. On SAE Standard Rotation (counterclockwise) engines, the balancer gear timing mark "B" must be in alignment with the center punch mark tooth (four, five or six punch marks) on crankshaft gear (3). On SAE Opposite Rotation (clockwise) engines, the balancer gear timing mark "R" must be in alignment with the "R" on the small idler gear. The other "R" on the small idler gear must be in alignment between the two marked teeth (with two punch marks) on the crankshaft gear. On 12 and 16 cylinder engines, no timing of the accessory drive gears is necessary.

SAE Standard Rotation 8 Cylinder Engine

SAE Opposite Rotation 8 Cylinder Engine.

Electrical System

Test Tools For Electrical System

Most of the testing of the electrical system can be done on the engine. The wiring insulation must be in good condition, the wire and cable connections must be clean and tight and the battery must be fully charged. If on the engine test shows a defect in a component, remove the component for more testing. The wire size, color and recommendations of length are given in the Wiring Diagrams in Systems Operation.

The service manual Testing And Adjusting Electrical Components, Form No. REG00636 has complete specifications and procedures for the components of the starting circuit and the charging circuit.

6V4930 Battery Load Tester

The 6V4930 Battery Load Tester is a portable unit in a metal case for use under field conditions and high temperatures. It can be used to load test all 6, 8 and 12V batteries. This tester has two heavy-duty load cables that can easily be fastened to the battery terminals, and a load adjustment knob on the front panel permits a current range up to a maximum of 700 amperes. The tester also has a thermometer to show when the safe operating temperature limit of the unit has been reached.

NOTE: Make reference to Special Instruction Form No. SEHS8268 for more complete information for use of the 6V4930 Battery Loader Test.

8T900 AC/DC Clamp-On Ammeter

The 8T900 AC/DC Clamp-On Ammeter is a completely portable, self-contained instrument that allows electrical current measurements to be made without breaking the circuit or disturbing the insulation on conductors. A digital display is located on the ammeter for reading current directly in a range from 1 to 1200 amperes. If an optional 6V6014 Cable is connected between this ammeter and one of the digital multimeters, current readings of less than 1 ampere can then be read directly from the display of the multimeter.

A lever is used to open the jaws over the conductor [up to a diameter of 19 mm (.75 in.)], and the spring loaded jaws are then closed around the conductor for current measurement. A trigger switch that can be locked in the ON or OFF position is used to turn on the ammeter. When the turn-on trigger is released, the last current reading is held on the display for 5 seconds. This allows accurate measurements to be taken in limited access areas where the digital display is not visible to the operator. A zero control is provided for DC operation, and power for the ammeter is supplied by batteries located inside the handle.

NOTE: Make reference to Special Instruction Form No. SEHS8420 for more information for use of the 8T900 Clamp-on Ammeter.

6V7070 Heavy-Duty Digital Multimeter

The 6V7070 Heavy-Duty Digital Multimeter is a completely portable, hand held instrument with a digital display. This multimeter is built with extra protection against damage in field applications, and is equipped with seven functions and 29 ranges. The 6V7070 Multimeter has an instant ohms indicator that permits continuity checking for fast circuit inspection. It also can be used for troubleshooting small value capacitors.

The 6V7800 Regular-duty Digital Multimeter (a low cost option to the Heavy-Duty Multimeter) is also available; however, the 6V7800 Multimeter does not have the 10A range or the instant ohms feature of the 6V7070 Multimeter.

NOTE: Make reference to Special Instruction Form No. SEHS7734 for more complete information for use of the 6V7070 and 6V7800 Multimeters.

Battery

Show/hide table

Never disconnect any charging unit circuit or battery circuit cable from battery when the charging unit is operated. A spark can cause an explosion from the flammable vapor mixture of hydrogen and oxygen that is released from the electrolyte through the battery outlets. Injury to personnel can be the result.

The battery circuit is an electrical load on the charging unit. The load is variable because of the condition of the charge in the battery. Damage to the charging unit will result if the connections (either positive or negative) between the battery and charging unit are broken while the charging unit is in operation. This is because the battery load is lost and there is an increase in charging voltage. High voltage will damage, not only the charging unit, but also the regulator and other electrical components.

Use the 6V4930 Battery Load Tester, the 8T900 Clamp-On Ammeter and the 6V7070 Multimeter to load test a battery that does not hold a charge when in use. See Special Instruction Form No. SEHS8268 for the correct procedure and specifications to use.

Charging System

The condition of charge in the battery at each regular inspection will show if the charging system operates correctly. An adjustment is necessary when the battery is constantly in a low condition of charge or a large amount of water is needed (more than one ounce of water per cell per week or per every 100 service hours).

When it is possible, make a test of the charging unit and voltage regulator on the engine, and use wiring and components that are a permanent part of the system. Off-engine (bench) testing will give a test of the charging unit and voltage regulator operation. This testing will give an indication of needed repair. After repairs are made, again make a test to give proof that the units are repaired to their original condition of operation.

Before the start of on-engine testing, the charging system and battery must be checked as shown in the Steps that follow:

1. Battery must be at least 75% (1.225 Sp. Gr.) fully charged and held tightly in place. The battery holder must not put too much stress on the battery.

2. Cables between the battery, starter and engine ground must be the correct size. Wires and cables must be free of corrosion and have cable support clamps to prevent stress on battery connections (terminals).

3. Leads, junctions, switches and panel instruments that have direct relation to the charging circuit must give correct circuit control.

4. Inspect the drive components for the charging unit to be sure they are free of grease and oil and have the ability to operate the charging unit.

Alternator Regulator Adjustment (Delco-Remy)

When an alternator is charging the battery too much or not enough, an adjustment can be made to the charging rate of the alternator.

Alternator Regulator Adjustment
(1) Voltage adjustment cap.

1. Remove voltage adjustment cap (1) from the alternator

2. Turn cap (1) 90° and install it again into the alternator. The voltage cap has four positions: HI, LO and two positions between the high and low settings.

- or -

3. Remove the covers from the end of the alternator to get access to the voltage regulator.

4. Remove the rubber from the potentiometer so that the small screw can be seen.

5. Connect a voltmeter across the batteries to measure the regulation of the voltage.

NOTE: The batteries must have a good charge for this measurement.

6. Operate the alternator at medium speed for 30 seconds and take a measurement of the voltage.

The voltage must be 27.4 volts. Turn the small screw counterclockwise to get less voltage output and clockwise to get more voltage output.

7. After the adjustment has been made, put a thin layer of silicone rubber sealant (3S6252) on the adjustment screw and install the covers.

NOTE: Make sure the location of the wires to the voltage regulator is not over the transistor pins. The transistor pins can make holes in the insulation for the wires and cause a short circuit.

Delco-Remy Regulator Adjustment
(1) Potentiometer adjustment screw. (2) Transistor pins.

Starting System

When the engine has a prelube system, check it first to be sure all components function correctly. See Prelube System. After checking the prelube system, put a wire temporarily between the connections of the oil pressure switch. This will let the following checks be made which is the same as checking engines that do not have a prelube system.

Use a D. C. Voltmeter to find starting system components which do not function.

Move the starting control switch to activate the starter solenoid. Starter solenoid operation can be heard as the pinion of the starter motor is engaged with the ring gear on the engine flywheel. The solenoid operation also closes the electric circuit to the motor. Connect one lead of the voltmeter to the solenoid connection (terminal) that is fastened to the motor. Ground the other lead. Activate the starter solenoid and look at the voltmeter. A reading of battery voltage shows the problem is in the motor. The motor must be removed for further testing. No reading on the voltmeter shows that the solenoid contacts do not close. This is an indication of the need for repair to the solenoid or an adjustment to be made to starter pinion clearance. Pinion clearance is 9.1 mm (.36 in.).

If the solenoid for the starter motor will not operate, current from the battery may not be getting to the solenoid. Fasten one lead of the voltmeter to the connection (terminal) for the battery cable on the solenoid. Ground the other lead. No voltmeter reading shows there is a broken circuit from the battery. Further testing is necessary when there is a reading on the voltmeter.

Further test by fastening one voltmeter lead to the connector (terminal) for the small wire at the solenoid and the other lead to the ground. Look at the voltmeter and activate the starter solenoid. A voltmeter reading shows that the problem is in the solenoid. No voltmeter reading shows that the problem is in the starter switch or wiring. Fasten one lead of the voltmeter to the battery wire connection of the starter switch and ground the other lead. A voltmeter reading indicates a failure in the switch.

A starter motor that operates too slow can have an overload because of too much friction in the engine being started. Slow operation of the starter motor can also be caused by shorts, loose connections and/or dirt in the motor.

Pinion Clearance Adjustment (Delco-Remy)

When the solenoid is installed, make an adjustment of the pinion clearance. The adjustment can be made with the starter motor removed.

1. Install the solenoid without connector (1) from the MOTOR connection (terminal) on solenoid to the motor.

2. Connect a battery, of the same voltage as the solenoid, to the terminal (2), marked SW.

Connection For Checking Pinion Clearance
(1) Connector from MOTOR terminal or solenoid to motor. (2) SW terminal. (3) Ground terminal.

3. Connect the other side of battery to ground terminal (3).

4. Connect for a moment, a wire from the solenoid connection (terminal) marked MOTOR to the ground connection (terminal). The pinion will shift to crank position and will stay there until the battery is disconnected.

5. Push the pinion toward commutator end to remove free movement.

6. Pinion clearance (6) must be 9.1 mm (.36 in.).

7. Pinion clearance adjustment is made by removing plug and turning nut (4).

Pinion Clearance Adjustment
(4) Shaft nut. (5) Pinion. (6) Pinion clearance.

Prelube System

The electrical components in this circuit are the pump motor, relay, oil pressure switch and starter switch. Install a wire around the oil pressure switch to test the components. This must be done with CAUTION.

Relay

Find the damaged component by first checking to see if there is AC current to the pump motor. Fasten a wire from the positive (+) side of the battery to the relay terminal (1) to complete the circuit through the relay coil. The relay must activate and complete the AC circuit and cause the pump motor to run. When this is done, run the pump long enough to make pressure show on the pressure gauge. During checks that will follow, engine parts will receive lubrication.

Remove the wire from around the oil pressure switch.

Checking Prelube System Relay
(1) Relay terminal.

Oil Pressure Switch

Prelube System Oil Pressure Switch
(1) Terminals.

With a wire installed between both terminals (1) of the oil pressure switch, engage the starter switch a moment. If the starter and solenoids engage, then the oil pressure switch has failed and must be replaced with a new switch. Leave the wire in place if the switch has not failed and check the starter switch.

Starter Switch

Use a wire installed between the starter battery terminal (2) and starter relay terminal (1). If the starter and solenoids engage, the failure is in the starter switch. If the starter switch has not failed, remove all wires that were installed for testing. See Starting System for further checks of the circuit components of the starting system.

Checking Starter Switch
(1) Starter relay terminal. (2) Starter battery terminal.

Low Emission Engines

Introduction

Low emission engines are designed to comply with the air pollution regulations as determined by various environmental agencies. These regulations control the amount of oxides of nitrogen, carbon monoxide and unburned hydrocarbons emitted by the engine exhaust into the air.

To meet requirements the G398 and G399 engines were designed run on a very lean air-fuel ratio. This lean air-fuel ratio combined with a high energy spark creates more complete combustion reducing the amount of pollutants emitted from the exhaust. In order to meet the low emission standards and maintain engine horsepower certain changes were made to the existing gas engines. The fuel system, ignition system and air induction and exhaust system are the major areas of change.

Description

The low emission engines are similar to the standard gas engines in appearance and in operation. The differences will be discussed in detail in the topics that follow.

Configuration

Both the G398 and G399 engines are high compression engines (10 to 1 ratio) turbocharged and aftercooled, and are equipped with watercooled exhaust manifolds. They are designed to run on dry natural gas. Refer to the chart Low Emission Timing Advance Information. Depending on the application a separate water circuit supplies either 32°C (90°F) or 54°C (130°F) water to the aftercoolers.

Fuel System

A different gas pressure regulator is needed to maintain a negative differential pressure between the gas pressure and the inlet air pressure to control the lean air-fuel ratio. Inlet gas pressure must be maintained from 145 to 220 kPa (21 to 32 psi) to the pressure regulator.

Ignition System

A different ignition system is used to deliver the high energy spark required to ignite the lean air-fuel ratio. Refer to Specifications for the static timing required for the low emission engines.

Air Induction And Exhaust System

In order to supply more air at higher inlet manifold pressures the differential pressure regulators (wastegates) were changed. Also the G398 inlet manifold was improved to provide more precise cylinder to cylinder fuel distribution.

Application

The low emission G398 and G399 engines can be utilized to add power to an existing site or to provide power for a new site and comply with local exhaust emission regulations.

Installation

There are many factors to be considered before the installation of an engine. Ambient air temperature and altitude will affect operation. There should be an adequate supply of natural gas and a source for water that will supply adequate cooling capacity for the engine and aftercooler. The information that follows will outline the steps necessary to ensure proper installation.

When operating at lean air-fuel ratios more air flow is required to produce the rated horsepower; therefore, there will be an increase in exhaust flow. The following charts show the inlet air flow in pounds per hour (lb/hr) and the exhaust flow in cubic feet per minute (cfm). These values are necessary to size the ventilation systems, mufflers and exhaust piping.

The affects of ambient air temperature changes must be held to a minimum. The separate circuit aftercooler water must be held to 32 ± 4° (90 ± 7°) or 54 ± 4° (130 ± 7°) to ensure that the air fuel ratio does not change. A temperature control valve must be installed in the aftercooler water circuit to regulate water flow. The schematic that follows illustrates how the thermostatically controlled valve should be installed.

(1) Radiator for aftercooler water. (2) AMOT valve. (3) Auxiliary water pump. (4) Aftercooler inlet. (5) Aftercooler outlet. (A) AMOT valve outlet. (B) AMOT valve bypass inlet. (C) AMOT valve normal inlet.

The altitude at which an engine is installed will affect performance. When the installation of the engine is over 152 m (500 ft.) above sea level one spacer should be removed from the pressure differential valve (wastegate) to maintain the correct horsepower rating. Refer to the instructions that follow before removing a spacer from the pressure differential valve.

Show/hide table

The pressure regulator cover is heavily spring loaded. To avoid personal injury do not deviate from the following procedure.

1. Remove the regulator from the engine.

2. Modify three 1B2716 (1/4-20 NC x 5 in.) bolts, by running a 1/4-20 NC die nut the full length of the bolts.

3. Remove three retaining bolts, one at a time, and replace each with a modified bolt to keep the cover contact surface parallel with the regulator body surface. Tighten the modified bolts enough to relieve pressure on the other two retaining bolts. Remove the two retaining bolts. Loosen the modified bolts alternately to relieve the spring tension.

4. Remove one spacer from between the valve body and cover.

5. Assemble the cover to the regulator body by using the modified bolts until the retaining bolts can be installed. Tighten the bolts to a torque of 6.3 ± 1.7 N·m (55 ± 15 lb ft).

Refer to the charts that follows to determine the altitude capabilities of the engines with one spacer removed. One spacer was removed for operation at 152 m (500 ft.) or more above sea level.

The combustion air flow for a low emission engine is considerably higher than the standard engine. Heat rejection values for the low emission engine are correspondingly higher and are shown in the following chart.

The values listed are for standard conditions. As the ambient temperature and altitude increase, the heat rejection also increases. Use the appropriate multiplier from the graphs that follow to obtain the design heat rejection value. For example, a G398 low emission engine applied at the 32°C (90°F) aftercooler water rating has an aftercooler heat rejection of 5,000 Btu/min. If the job site is at 1219 m (4000 ft.) and the maximum ambient temperature expected is 38°C (100°F), the multiplier is approximately 1.34. The actual heat rejection at this altitude and ambient temperature would be 5000 x 1.34 = 6700 Btu/min. This value does not allow for any deterioration in cooling capacity of the heat exchanger used to cool the aftercooler water. Good design practice would add 10% to the actual heat rejection when sizing a heat exchanger.

Aftercooler Heat Rejection Factors 32°C (90°F) Water To Aftercooler

Aftercooler Heat Rejection Factors 54°C (130°F) Water To Aftercooler

The correct air-fuel ratio adjusted on site will be based on the temperature of the fuel at the time of adjustment. If the Btu content of the fuel remains constant, a variation in fuel temperature of ± 14°C (25°F) can be tolerated. If the Btu content varies, closer tolerance will be necessary. If the fuel temperature cannot be held within these limits, a heat exchanger for the fuel gas must be designed into the aftercooler water circuit such that the temperature control valve controlling water temperature to the aftercooler will also control water to the fuel gas heat exchanger. The illustration that follows shows where the fuel heat exchanger can be installed.

(1) Radiator for aftercooler water. (2) AMOT valve. (3) Auxiliary water pump. (4) Aftercooler inlet. (5) Aftercooler outlet. (6) Fuel heat exchanger. (A) AMOT valve outlet. (B) AMOT valve bypass inlet. (C) AMOT valve normal inlet.

The adjustments made on the site to obtain the correct air-fuel ratio will be correct only for the composition of fuel at the time. A maximum of ± 5% Btu variation of the fuel at constant temperature can be tolerated before encountering combustion problems. If the LHV of the fuel varies more than 5%, manual adjustments must be made to return to the correct air-fuel ratio. The fuel gas source must be evaluated to ensure the LHV of the fuel will not vary more than ± 5% to avoid unstable or damaging operating conditions.

Operation

After the engine has been properly installed on the site and the fuel content and temperature have been checked as explained in the topic Installation, the engine should start with adjustments from the last engine test. See the topic, Start-up Procedure.

Start-up Procedure

1. Follow the standard start-up and troubleshooting procedures.

2. After the engine is started allow the engine to warm up to normal operating temperatures and set the engine at its rated rpm. With the engine under full load the pressure differential in the pressure regulator should read approximately -.6 in. H₂O.

3. Using a suitable O₂ meter set the O₂ levels as follows:

a. Refer to the appropriate chart (Figures 1 through 4) for this engine configuration to determine the proper O₂ level.

b. Adjust power adjustment knob on each carburetor until the O₂ level matches the number found on the O₂ emission graph.

c. The difference of O₂ levels between the two banks must not exceed .1%.

NOTE: It is important that the O₂ levels read as outlined in steps b. and c. above. If the mixture is too rich (O₂ levels below the % level determined in step b.) there could be possibly engine detonation or overload. If the mixture is too lean (O₂ levels above the % determined in step b.) power loss, poor response, part throttle instability, misfire, or a combination of these problems could result.

4. Measure the boost in the intake manifolds to determine the power level. Refer to the charts (Figures 1 through 4) for horsepower at specific boost levels.

5. If the O₂ levels are correct and the engine is operating at rated horsepower, the engine is adjusted properly.

6. After 150 hours of operation the adjustments should be checked and readjusted, if necessary, due to the break-in period of the engine.

Figure 1

Figure 2

Figure 3

Figure 4

Troubleshooting

The troubleshooting information for the standard gas engines applies to these engines, but because the air-fuel ratio is more critical on these engines certain areas require closer attention.

Problem 1: High Boost, Misfires, Hard Starting

Probable Cause:

1. Carburetor out of adjustment:

Adjust power control knob toward the "R" (richer).

2. Pressure regulator out of adjustment:

Turn nut CCW until symptom disappears.

3. Low fuel pressure to the regulator:

Fuel pressure to the regulator should be 145 to 220 kPa (21 to 32 psi).

Problem 2: Detonation, Low Boost, High Exhaust Temperature

Probable Cause:

1. Carburetor out of adjustment:

Adjust power control knob toward the "L" (leaner).

2. Pressure regulator out of adjustment:

Turn nut CW until symptom disappears.

₂₂ Problem 3: O Level Varies More Than ± .1% From Specified O Level On Emission Graph

Probable Cause:

1. Fuel temperature varies too much:

Add a fuel heat exchanger to hold temperature to ± 14°C (25°F).

2. Fuel BTU content varies more than ± 5%:

Compensate by holding fuel temperature to a closer tolerance than ± 14°C (25°F).