1673 DIESEL TRUCK ENGINE Caterpillar

Testing And Adjusting


Problem Solving

1. Engine Fails to Start
2. Misfiring
3. Stalls at Low Speed
4. Erratic Engine Speed
5. Low Power
6. Excessive Vibration
7. Heavy Combustion Knock
8. Valve Train Clicking Noise
9. Oil in Coolant
10. Mechanical Knock
11. Excessive Fuel Consumption
12. Loud Valve Train Noise
13. Little Rocker Arm Movement and Excessive Lash
14. Spring Retainer Free
15. Slobber
16. Valve Lash Close-Up
17. Premature Engine Wear
18. Coolant in Engine Lubricating Oil
19. Excessive Black or Grey Smoke
20. Excessive White or Blue Smoke
21. Low Engine Oil Pressure
22. High Lubricating Oil Consumption
23. Abnormal Engine Coolant Temperature

Air Induction And Exhaust System

Restriction Of Air Inlet And Exhaust

Engine horsepower and efficiency will be reduced if either the air inlet or exhaust system becomes restricted.

The air cleaner should not restrict air flow to the point of 30" (762 mm) of water difference in pressure.

Exhaust back pressure (pressure difference measured between the turbocharger outlet elbow tap and the ambient air) should be no more than 15" (381 mm) of water, difference in pressure.

Measuring Inlet Manifold Pressure

When an engine is suspected of lacking power, it is sometimes desirable to make a quick instrument check to determine the approximate horsepower.

By checking inlet manifold pressure, and comparing that pressure with the RACK SETTING INFORMATION, one can determine if an engine is operating efficiently. This test should be used if engine horsepower seems to be too low, yet no specific symptom of engine trouble is apparent.

Inlet manifold pressures in the RACK SETTING INFORMATION are recorded under specific operating conditions: 29.4 inches (746,76 mm) of mercury barometric pressure, 85° F. (29.4° C.) ambient temperature and 35 API rated fuel. Any deviation from these conditions can affect the inlet manifold pressure. Ambient air which is denser than that at 85°F./29.4 inches (29.4°C./746,76 mm) of mercury, can cause a slightly higher horsepower and inlet manifold pressure reading than listed in the RACK SETTING INFORMATION. If the ambient air is less dense, the horsepower and inlet manifold pressure rating can be slightly lower than the values given in the RACK SETTING INFORMATION. Fuel density (API gravity rating) also affects the horsepower and inlet manifold pressure. If the fuel is rated above the standard 35 API gravity rating, the inlet manifold pressure can be slightly less than the value given in the RACK SETTING INFORMATION. If the fuel is rated below the standard rating, the inlet manifold pressure can be slightly more. Be sure the air inlet and exhaust are not restricted when checking inlet manifold pressure.

The components in a 4S6553 Instrument Group provide a means of reading engine RPM and inlet manifold pressure simultaneously. This group contains an instantaneous reading tachometer and a gauge for reading inlet manifold pressure. Instructions (FE036044) included with this group, explain the testing procedure.

Checking Inlet Manifold Pressure At Engine Full Load And Speed

4S6553 Instrument Group.

Checking inlet manifold pressure (frequently referred to as "boost") at engine FULL LOAD and speed (governor balance point), provides a convenient test of engine performance. To check inlet manifold pressure, some method of loading the engine must be provided. The preferred method is by using a chassis dynamometer. An alternate method of loading the engine is to pull a loaded trailer, and use the brakes.

Using the 4S6553 Instrument Group, proceed as follows:

1. Connect the manifold pressure gauge to the inlet manifold.

1-Location to check inlet manifold pressure.

2. Connect the tachometer to the engine to locate the full load RPM (governor balance point).

NOTE: At the balance point, rack position and the injection pump speeds are such that maximum fuel is delivered to the engine, turbocharger speed is maximum, and inlet manifold pressure is maximum.

3. With the accelerator fully depressed, load the engine until engine RPM stabilizes. Slowly decrease the load (allowing engine RPM to increase) while simultaneously observing the rise in inlet manifold pressure.

NOTE: Inlet manifold pressure will rise (as load is decreased), reach a peak, and fall sharply. Watch for the pressure peak and note the RPM at which it occurs. This RPM is the governor balance point.

4. Record the engine RPM and inlet manifold pressure.

5. Return accelerator to low idle.

6. Compare the recorded information, engine RPM and inlet manifold pressure, with the values listed in the RACK SETTING INFORMATION book. If both values are within their specified limits, engine output is within expected limits.

7. If full load RPM and/or inlet manifold pressure are outside their limits, determine the cause and correct. See topic PROBLEM SOLVING - ENGINE - TESTING and ADJUSTING.

Crankcase Pressure

Excessive crankcase pressure can be a result of combustion gas leaking past broken or damaged pistons and/or piston rings. This condition will usually be accompanied by irregular engine operation and excess fumes from crankcase breather opening. This pressure can cause the breather element to become restricted in an unusually short time. In addition, it can cause engine oil to leak past gaskets and seals that would function properly under normal conditions.

Cylinder Head


Irregular (rough) engine operation can be caused by improperly adjusted or leaky valves. Operate the engine at the RPM which makes the malfunction most pronounced. A non-firing or low compression cylinder can be located by momentarily loosening and then retightening fuel lines at the fuel injection pumps one at a time. Continue this until a loosened fuel injection line makes little or no difference in the engine operation. This same test can also indicate faulty fuel injection so further checking of the cylinder is necessary.

The preceding test is merely a quick means of pinpointing the source of cylinder compression loss. Removal of the head and visual inspection of the valves and seats is necessary to check for minor valve defects which do not have much effect on engine operation. This is usually done during general engine reconditioning.

The following procedure provides a more complete check of the sealing ability of the individual valves without removing the cylinder head:

1. Remove the fuel injection nozzle, leaving the precombustion chamber in place.

2. Adapt an air hose to the precombustion chamber. This can be done with either a threaded fitting or by holding a rubber adapter in place.

3. Rotate the crankshaft until the piston in the suspected cylinder is at top center (TC) on the compression stroke. In this position the valves of this cylinder are closed.

4. Force air into the cylinder and then check for escaping air. Air escaping from the exhaust opening indicates exhaust valve leakage. Air escaping from the air cleaner inlet indicates inlet valve leakage. If air escapes from the crankcase breather during this test, the piston, rings and/or liner can be at fault.

It may be necessary to remove inlet and outlet connections on both sides of turbocharger to notice leakage.

Valve Clearance Setting

1. Remove the valve cover. Rotate the engine flywheel so the flywheel timing pointer is at TC 1-6 cyl. on the flywheel.

2. Observe the positions of the No. 1 and No. 6 cylinder valves to determine which cylinder is sealed for compression.

3. All exhaust and inlet valve clearance can be adjusted by positioning the flywheel only twice. After adjusting half of the valves, rotate the flywheel 360° and adjust the remaining half. If No. 1 cylinder is in compression, adjust the inlet valve clearances for cylinders 1, 2 and 4, and the exhaust valve clearances for cylinders 1, 3 and 5. If No. 6 cylinder is in compression, adjust the inlet valve clearances for cylinders 3, 5 and 6 and the exhaust valve clearances for cylinders 2, 4 and 6.

Fuel System

Difficulty within the fuel system can be classed in one of two groups: lack of fuel or too much fuel for proper combustion.

Many times the fuel system is blamed when the fault lies elsewhere, especially when smoky exhaust is the problem. Smoky exhaust can be the result of a faulty fuel injection valve, but it can also be caused by lack of air for complete combustion, overloading at high altitude, excessive oil burning or lack of compression.

Visual Inspection

1. Observe the fuel pressure gauge reading. Lack of pressure indicates difficulty in the supply side of the system.

2. Check the fuel level in the supply tank and the fuel tank cap vent for being plugged.

3. See that the vent valve is closed.

4. Check for leakage in the fuel supply lines and components or for a kinked or restricted supply line.

5. Replace the fuel filter element and clean the primary fuel filter.

6. Inspect the fuel bypass valve to see that it moves freely and that dirt is not holding the plunger off its seat. Be certain the spring has proper tension.

7. Bleed the fuel system to remove trapped air.

Fuel Injection Service

When installing a fuel injection valve, always check the seats of both the nozzle and the precombustion chamber. The nozzle assembly should be only finger-tight on the body. It is important to maintain the nozzle retaining nut torque to 105 ± 5 lb. ft. (14,5 ± 0,7 mkg). Excessive torque will damage the nozzle. Less torque will allow the nozzle to leak and may cause the nozzle case to bulge or split.

Positioning the fuel rack with the 7S7113 Rack Setting Gauge (1). The gauge is installed on the flange of the accessory drive housing.

The fuel rack must be held at the center or "zero" position while removing or installing a fuel injection pump. An injection pump installed in the "fuel on" side of its gear segment can cause the engine to overspeed with resultant serious damage to the engine and driven equipment.

The rack is positioned at the center or "zero" position by setting the gauge to .000" and moving the rack forward until it contacts the gauge.

When removing fuel injection pumps, spacers and lifters, the components should be kept together and marked so they can be installed in their respective location.

While disassembling fuel injection pumps, exercise considerable care to prevent damage to the plunger surfaces. The barrel and the plunger assembly are matched and the individual parts are not interchangeable with other barrels or plunger assemblies. Use extreme care when inserting the plunger into the bore of the barrel.

When a fuel injection pump is installed properly, the retaining bushing can be screwed-in finger-tight, flush with the top of the fuel injection pump housing. If the bushing cannot be turned flush with the top of the housing, the notch in the bonnet is not aligned with the dowel in the housing. It is important to maintain the final tightening torque of the retaining bushing to 150 ± 10 lb. ft. (20,7 ± 1,4 mkg). With a torque value of less than that required, the pump will leak. If the torque value is greater, the housing can be damaged.

Testing Fuel Injection Equipment

Before attempting to test a fuel injection pump or valve from an engine that is missing or puffing black smoke, a simple check can be made to determine which cylinder is causing the difficulty. With the engine running at a speed which makes the defect most pronounced, momentarily loosen the fuel line nut on the injection pump sufficiently to "cut out" the cylinder. Check each cylinder in the same manner. If one is found where loosening makes no difference in the irregular operation or causes puffing or black smoke to cease, the pump and valve for only that cylinder need be tested.

Checking Fuel Injection Valve

Examine fuel injection valves for:

1. Excessive carbon on tip of nozzle or in orifice.
2. Erosion of the orifice.
3. Screen plugged with dirt.

The condition of a capsule-type nozzle assembly can be tested on the Caterpillar Diesel Fuel Injection Test Apparatus, and the rate of leakage of the nozzle assembly can be determined.

Checking Fuel Injection Pump Lifter Washer and Pump Plunger

The timing dimension should be checked to compensate for wear in the timing gears or lifters. This will assure that the point of the fuel injection is correct. If the timing dimension is too small, injection will begin early, and if too great, injection will be late.

When pump plunger wear becomes excessive, the lifter washer may also be worn so it will not make full contact with the end of a new plunger. To avoid rapid wear on the end of the new plunger, replace the lifters having washers showing visible wear.

These are patterns of wear between washer and plunger. Fig. A illustrates the contact surfaces of a new pump plunger and a new lifter washer. In Fig. B the pump plunger and lifter washer have worn considerably. Fig. C shows how the flat end of a new plunger makes poor contact with a worn lifter washer, resulting in rapid wear to both parts.

A pump can maintain a satisfactory discharge rate and yet be unserviceable because of delayed timing resulting from wear on the lower end of the plunger. When testing a pump which has been in use for a long time, check the plunger length with a micrometer. Discard the pump if the plunger measures less than the minimum length (worn) dimension.

Inspect the upper diameter of the plunger for wear. The performance of pumps worn in this manner can be checked as described in the Instructions for Fuel Injection Test Apparatus.

Fuel System Adjustments

8S7167 Gauge.6F6922 Depth Micrometer with a 4 to 5 in. (101,6 to 127,0 mm) rod.1F8747 Plate Assembly.2M5218 Shaft in place of 7F8751 Shaft.2M5220 Pointer Assembly.8S5417 Timing Plate.8S5132 Puller Plate.8S6470 Pressure Screw.8S5133 Expansion Plug.8S8375 Sleeve.8S8561 Step Plate.

Locating Top Dead Center Compression Position For No. 1 Piston

No. 1 piston on the compression stroke at top center (TC) is the reference point for all timing procedures.

Remove the valve and rocker arm cover (the two valves at the front of the engine are the inlet and exhaust valves for No. 1 cylinder). Remove timing pointer cover (1).

This illustrates location of timing pointer cover (1).

Rotate the crankshaft counterclockwise (as viewed from the flywheel end) at least 60°. Continue rotating the crankshaft counterclockwise until the TC1-6 cyl. mark on the flywheel is aligned with the pointer and both the inlet and exhaust valves of No. 1 cylinder are closed.

Fuel Pump Timing Dimension Setting - On Engine

The timing dimension should be checked and reset, if necessary, to account for worn timing gears or worn pump lifters. The timing dimension can be set in the following manner:

1. Locate (TDC) compression position for No. 1 piston. Refer to the topic LOCATING TOP DEAD CENTER COMPRESSION POSITION FOR No. 1 PISTON.

2. Remove No. 1 fuel pump. Insert an 8S4618 Gauge into the fuel pump bore.

3. With gauge seated in fuel pump housing, the higher step of the plunger must be slightly above the top surface of the gauge. The lower step of the plunger must be just below the top surface of the gauge.

4. If the plunger in the gauge is not in the position stated in Step 3, adjust the lifter setting using the following procedure.

5. Remove the small cover from the front of the timing gear cover, and loosen the accessory drive gear retaining nut.

This illustrates the 8S4618 Gauge installed.

This is a cross-sectional view of the 8S4618 Gauge installed.

6. Separate the gear from the accessory drive shaft.

Separating the gear from the accessory drive shaft. Tools required: 8S5132 Puller Plate, 8S8375 Sleeve, 8S5133 Expansion Plug, 8S6470 Pressure Screw, 8B7561 Step Plate, two 3/8" NF bolts 31/2 in. (88,9 mm) long, two 3/8" flat washers.

7. Turn the accessory drive shaft extension nut counterclockwise until the lower step of the plunger is even with the top of the gauge.

Typical example of setting fuel pump timing dimension.

8. Tighten the accessory drive gear retaining nut to 100±10 lb. ft. (13,8±1,4 mkg) and again check the lifter setting with the gauge.

NOTE: If preferred, use the 8S7167 Gauge and a 6F6922 Depth Micrometer with a 4 to 5 in. (101,6 to 127,0 mm) rod to check the timing dimension. The dimension should be 4.2159-4.2199 (107,08-107,18 mm).

Checking timing dimension setting with: 1-Spacer. 2-8S7167 Gauge. 3-6F6922 Depth Micrometer, 4 to 5 in. (101,6 to 127,0 mm) rod. The timing dimension is indicated by "A".

Fuel Pump Timing Dimension Setting - Off Engine

Proceed with off engine timing using an 8S7167 Gauge, 6F6922 Depth Micrometer, 4 to 5 in. (101,6 to 127,0 mm) rod, 1F8747 Plate Assembly (with a 2M5218 Shaft in place of the standard 7F8751 Shaft) and a 2M5220 Pointer Assembly.

1. Install the pointer assembly on the fuel injection pump housing.

2. Place the timing plate on the drive end of the camshaft. Secure the plate to the camshaft.

3. Refer to the chart and select the timing plate degree setting for the lifter being checked or set. Set the timing plate by rotating it counterclockwise until the proper degree setting aligns with the pointer assembly. Lock in position with the lockscrew.

4. The fuel injection pump timing dimension (off engine), using the 8S7167 Gauge is 4.2670-4.2680 in. (108,38-108,40 mm).

5. The spacer must be changed to change the timing dimension.

6. If all timing dimensions are to be checked or reset, continue the same procedure in the firing order of the engine. Recheck each timing dimension after the adjustment has been made, to make sure the dimension is correct.

NOTE: The accessory drive shaft must be positioned correctly in relation to the engine crankshaft, before the fuel injection pump housing is installed on the engine. See the topic FUEL INJECTION PUMP CAMSHAFT TIMING.

Fuel Injection Pump Camshaft Timing

NOTE: The fuel injection pump housing must be removed and the engine crankshaft positioned with No. 1 piston on the compression stroke at top center (TC).

1. Install the 8S5417 Timing Plate on the rear face of the accessory drive housing, dowels aligned and bolts installed as illustrated.

8S5417 Timing Plate installed on accessory drive housing.

NOTE: If the timing plate can be installed, timing is correct. If it cannot be installed, proceed as follows.

2. Remove the small cover from the front of the timing gear housing. Loosen the gear retaining nut (do not remove the nut).

Separating the gear from the accessory drive shaft. Tools required: 8S5132 Puller Plate, 8S8375 Sleeve, 8S5133 Expansion Plug, 8S6470 Pressure Screw, 8B7561 Step Plate, two 3/8" NF Bolts 31/2" (88,9 mm) long, two 3/8" flat washers.

Rotating the accessory drive shaft.

3. Separate the gear from the accessory drive shaft.

4. Rotate the accessory drive shaft in the direction necessary to install the 8S5417 Timing Plate.

5. Tighten the gear retaining nut to a torque value of 100±10 lb. ft. (13,8±1,4 mkg) and remove the timing plate. The fuel injection pump camshaft will be in time with the engine crankshaft when the injection pump housing is installed on the engine.

Fuel Rack Setting-Using The 8S2349 Rack Positioning Tool Group And 9M9268 Dial Indicator

The 8S2349 Rack Positioning Tool Group makes it possible to set the rack, or measure rack position, during normal operation of the engine. The ability to observe rack position during operation, can provide much of the needed data to determine actual horsepower output and diagnose the cause for lack of power.

9M9268 Dial Indicator shown is not a part of the 8S2349 Rack Positioning Group. Parts in this group are: 1-8S2351 Bracket. 2-8S2354 Rod. 3-8S2355 Spacer. 4-8S2356 Hole Attachment.

1. Refer to the RACK SETTING INFORMATION to obtain the correct rack setting dimension.

2. Remove the fuel rack cover and gasket from the front of the flange on the accessory drive housing. Install the dial indicator and rack positioning tool on the engine.

3. Place the spacer over the rod in the bracket. Adjust the dial on the indicator to read zero when the hole attachment is against the rod and the rod is against the spacer.

4. Before starting the engine, be sure the rack moves freely throughout its entire length of travel. The speed limiter will restrict rack travel until the engine is operating with proper oil pressure, or the plunger is manually depressed.

5. To adjust the rack, stop the engine and remove the cover at the rear of the governor housing.

Insert a shim or thickness gauge of the correct thickness, between the torque spring and stop bar. Rotate the governor control shaft in the fuel-on direction, until the rack stop collar adjustment screw is against the torque spring.

Typical example of dial indicator adjusted to zero reading: 3-8S2355 Spacer. 4-8S2356 Hole Attachment.

6. Loosen lock nut (6) and using wrench (7), adjust screw (5) to obtain the correct rack setting. Refer to the RACK SETTING INFORMATION. Rack travel can be read directly on the 9M9268 Dial Indicator.

NOTE: Turn screw (5) clockwise to decrease rack travel. Never adjust rack travel by adding or removing shims.

7. After the rack has been adjusted, tighten lock nut (6) to 11±1 lb. ft. (1,5±0,14 mkg)

5-Adjusting screw. 6-Lock nut. 7-4B9820 Wrench. 8-8H8581 Thickness Gauge.

Governor Adjustments


Only competent personnel should attempt to adjust the low and high idle RPM. The low and high idle RPM, and the rack setting dimensions for this engine, are listed in the RACK SETTING INFORMATION.

Engine RPM should be checked with an accurate tachometer.

Low and high idle RPM can be adjusted by removing the cover at the rear of the governor, and turning the high idle and low idle adjusting screws. Turning either adjusting screw in a clockwise direction will decrease the respective high and low idle RPM. The retainer holes in the cover are shaped to prevent the screws from turning, after the adjustment has been made.

Typical example of parts involved in making governor adjustments are: 1-Cover. 2-Retainer holes (two). 3-High idle adjusting screw. 4-Low idle adjusting screw.

After setting the idle RPM, move the governor control lever to change the engine RPM. Return it to the idle position and recheck the idle RPM. Repeat the adjustment procedure until the specified idle RPM is obtained.

Fuel Rack Setting-Using The Rack Setting Gauge

Use a 7S7113 Rack Setting Gauge to check the fuel rack setting. The fuel rack can be checked and adjusted with the fuel injection pump housing either installed, or removed from the engine.

1. Remove the rack cover from the front of the accessory drive housing rear flange and the cover from the rear of the governor housing.

This view illustrates the installation of 7S7113 Rack Setting Gauge.

2. Install the 7S7113 Rack Setting Gauge over the front end of the fuel rack.

3. Set gauge to the proper rack setting. Refer to the RACK SETTING INFORMATION for correct setting.

4. To adjust the rack, refer to the topic FUEL RACK SETTING - USING THE 8S2349 RACK POSITIONING TOOL GROUP AND 9M9268 DIAL INDICATOR and follow Steps 5, 6 and 7.

Fuel Ratio Control Setting

The fuel rack must be set correctly before setting the fuel ratio control. See the topic FUEL RACK SETTING.

1. Remove the rack cover from the front of the fuel injection pump housing, and cover (4) from the rear of the fuel ratio control.

1-Cover. 2-Opening. 3-Small pry.

2. Install a 7S7113 Rack Setting Gauge over the front end of the fuel rack and set the gauge to a reading of +.020".

3. Engage slot in cover (4) with cross-dowel in adjusting bolt and turn the adjusting bolt in as far as possible. This prevents the head of the bolt from limiting the travel of the fuel rack.

4. Remove the plug from the bottom of the governor. Through opening (2), use a small pry (3) to push in (retract) the speed limiter plunger.

5. With the speed limiter plunger held in, move governor control lever to FULL LOAD position. Hold the lever in the FULL LOAD position while making the adjustment.

6. Through opening (5) move the collar toward the rear until spring resistance is felt. Using cover (4), turn adjusting bolt out until the head just contacts the collar.

NOTE: With the collar positioned toward the rear of the governor, adjusting bolt contact with the collar can be observed through opening (5). (As the bolt head contacts collar, movement of the collar can be seen and spring resistance can be felt).

4-Cover. 5-Opening.

7. Turn cover (4) clockwise the amount necessary to align the bolt holes and install cover (4).

8. Install cover (1) over opening (5). Remove the 7S7113 Rack Setting Gauge and install the rack cover.

9. Install the plug in opening (2).

NOTE: Before starting the engine, make certain the governor control lever, or accelerator pedal, will move the governor to the SHUTOFF position and that all parts operate freely.

When the engine is in use, and exhaust smoke is apparent on acceleration, smoke can be reduced by resetting the fuel ratio control. Reset the control by using cover (4) to turn adjusting bolt out (less fuel) 1/2 turn. If smoke is still evident, repeat the procedure until smoke is acceptable and acceleration is still satisfactory.

NOTE: Some exhaust smoke is likely to appear at maximum acceleration.

When exhaust smoke is acceptable but acceleration is sluggish, the control can be reset by using cover (4) to turn adjusting bolt in (more fuel) 1/2turn. If acceleration is still sluggish, repeat the procedure until operation is satisfactory.

NOTE: If acceleration is sluggish and full engine power seems to be lost, inspect the air line to the cover and the cover gasket for air leaks. If no air leaks are apparent, inspect the diaphragm. A damaged diaphragm will not allow the fuel rack to open completely, acceleration will be sluggish and full engine power cannot be obtained.

Cooling System

The engine has a pressurized cooling system. Pressurizing the cooling system serves two purposes. First, it permits safe operation at coolant temperature higher than the normal boiling point; thereby, providing a margin of cooling for those intermittent peak loads. Secondly, it prevents cavitation in the water pump and reduces the possibility of air or steam pockets forming in the coolant passages.

Many times, overheating of the engine is caused by failure to make simple systematic inspections. Visual inspections should be made before instrumentation testing.

Visual Inspection

1 Check coolant level.

2 Inspect for leaks in the system.

3 Inspect the radiator fins. Be certain the air flow through the radiator is not restricted by trash or bent radiator fins.

4 Check fan belts.

5 Check for damaged fan blades.

6 Observe if there is any air or combustion gas in the cooling system.

7 Check to see that the radiator cap sealing surfaces are clean.

Testing Cooling System Controls

Remember that temperature and pressure go hand-in-hand and neither one can be tested logically without considering the other. For example, the effect of pressurization and altitude on the boiling point of water is shown in the chart.

Temperature Gauge

2F7112 Thermometer,6B5072 Bushing.

If overheating and loss of coolant is a problem, a pressure loss in the system could be the cause. If an overheating condition is indicated on the temperature gauge and loss of coolant is not evident, check the accuracy of the temperature gauge. Make this check by installing a 2F7112 Thermometer with a 6B5072 Bushing into the cylinder head.

This illustrates the installation of the 2F7112 Thermometer (1) and 6B5072 Bushing (2).

------ WARNING! ------

Use CAUTION when working around moving parts with the engine running.


Start the engine. Cover the radiator to reduce air flow and cooling. The reading on the instrument panel gauge should agree with the reading on the 2F7112 Thermometer.

Radiator Filler Cap

If the pressure check indicates that the system is unable to hold pressure, the source of the pressure leak must be determined. One of the causes of cooling system pressure loss can be a faulty radiator cap seal. Inspect the radiator cap carefully for possible damage to the seal or sealing surfaces. The build-up of deposits on the cap, seal and filler neck should be removed.

Water Temperature Regulator

The opening temperature of the regulator (bench test in atmospheric pressure) should be approximately 165±1°F (74±1°C). The regulator should be fully open at approximately 180°F (85°C).

1. Remove the regulator from the cylinder head.

2. Suspend the regulator and a thermometer in a pan of water as shown.

3. Apply heat to the pan and stir the water to maintain uniformity.

4. Observe the opening temperature of the regulator.

If the regulator does not operate correctly, install a new regulator.

Testing water temperature regulator.

Cleaning The Cooling System

It is advisable to periodically clean the cooling system. To clean the cooling system, start the engine and allow the coolant to reach operating temperature, then proceed as follows:

1. Stop the engine and drain coolant as soon as possible.

2. Close drains and degrease the cooling system if grease is evident in the top tank. Fill the cooling system using two and one-half pounds of Sal Soda to every ten gallons of water.

3. Start the engine and run it at operating temperature for at least ten minutes.

4. Stop the engine, drain and flush the system thoroughly. Any significant amount of Sal Soda solution left in the cooling system, will decrease the effectiveness of the following cleaning procedure.

5. Fill the system with a solution of one pound of Oxalic Acid or Sodium Bisulfate to every five gallons of water.

6. Start the engine and run it at operating temperature for 30 to 60 minutes. Stop the engine. Drain and flush the cooling system until water is clear.

7. Fill the cooling system with a solution of one-half pound of Sal Soda for every ten gallons of water, and then run the engine for ten minutes.

8. Drain, flush, and fill the system with fresh water and corrosion inhibitor, or the desired amount of anti-freeze.

Electrical System

Most of the electrical system testing can be performed on the vehicle. The wiring insulation must be in satisfactory condition, the wire and cable connections both clean and tight and the battery fully charged. It should be remembered an "on-vehicle" test usually indicates a component must be removed for further testing.


A load test should be made on a battery that discharges very rapidly when in use. To do this apply a resistance of three times the ampere/hour rating of the battery across the battery main terminals. Allow the resistance to discharge the battery for 15 seconds and immediately test the battery voltage. A 6 volt battery in good condition will test 4.5 volts; a 12 volt battery in good condition will test 9 volts and a 24 volt battery will test 18 volts.

Starting System

Use a D.C. voltmeter to locate starting system components which do not function.

Turn the key switch ON. Turn the HEAT-START switch to the START position. Starting motor solenoid operation is audible as the starter motor pinion engages with the ring gear on the engine flywheel. The solenoid operation should also close the electric circuit to the motor. Attach one voltmeter lead to the solenoid terminal that is connected to the motor. Ground the other lead. Turn the HEAT-START switch to START and observe the voltmeter. A battery voltage reading indicates the malfunction is in the motor. It must be removed for further testing. No voltmeter reading indicates that the solenoid contacts do not close and the solenoid must be repaired or the starter pinion clearance should be adjusted to .36 in. (9,14 mm). See topic PINION CLEARANCE ADJUSTMENT.

A starting motor solenoid that will not operate may not be receiving battery current. Attach one lead of the voltmeter to the solenoid battery cable connection. Ground the other lead. No voltmeter reading indicates a faulty circuit from the battery. A voltmeter reading indicates further testing is necessary.

Continue the test by attaching one voltmeter lead to the starting motor solenoid small wire terminal and the other lead to ground. Observe the voltmeter and turn the HEAT-START switch to START. A voltmeter reading indicates that the malfunction is in the solenoid. No voltmeter reading indicates that either the series parallel switch is the fault or the HEAT-START switch does not close when turned to the START position.

Attach one lead of the voltmeter to the HEAT-START switch battery wire terminal and ground the other lead. A voltmeter reading indicates a defective switch. No voltmeter reading indicates further testing of the series-parallel switch is necessary.

A starting motor that operates too slow can be overloaded by excessive mechanical friction within the engine being started. Slow starting motor operation can also be caused by shorts, loose connections and/or excessive dirt within the motor.

Glow plugs can be checked with an ammeter. Disconnect the wire lead from the glow plug terminal on the HEAT-START switch. Install an ammeter, in series, between the disconnected lead and the terminal on the switch. Observe the ammeter with the HEAT-START switch turned to the HEAT position. Each 12 volt glow plug draws approximately 10 amperes. The ampere draw of one glow plug multiplied by the number of engine cylinders will be the total ampere draw of the glow plugs in the engine. A low reading is an indication of one or more defective glow plugs. Disconnect one glow plug lead at a time and observe the ammeter with the switch turned to HEAT. The disconnected glow plug that does not change the ammeter reading is the defective glow plug.

When no ammeter reading is obtained, test the HEAT-START switch. Attach one lead of the voltmeter to the glow plug wire terminal on the HEAT-START switch and the other lead to the ground. Observe the voltmeter and turn the switch to HEAT. No voltage indicates that the HEAT-START switch is defective.

Pinion Clearance Adjustment

Whenever the solenoid is installed, the pinion clearance should be adjusted. The adjustment should be made with the starting motor removed.

Bench test and adjust the pinion clearance at installation of solenoid as follows:

Specific points related to the circuit connections for checking pinion clearances are: 1-Connector from MOTOR terminal on solenoid to motor. 2-SW terminal. 3-Ground terminal.

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

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

3. Connect the other side of battery to ground terminal or to solenoid frame.

4. MOMENTARILY flash a jumper wire from the solenoid terminal marked MOTOR to the frame or ground terminal. The pinion will shift into cranking position and will remain there until the battery is disconnected.

This schematic shows the circuit for checking and adjusting pinion clearance. 2-SW terminal. 3-Ground terminal. 4-Ground flashing point.

5. Push pinion towards commutator end to eliminate free movement.

6. Pinion clearance should be .36 in. (9,14 mm).

7. Adjust clearance by removing plug and turning shaft nut.

This illustrates the points where pinion clearance checking and adjusting are made. 5-Pinion. 6-Pinion clearance. 7-Shaft nut.

Charging System

The condition and state of charge of the battery at each regular inspection will indicate if the alternator is operating efficiently. An adjustment is necessary when the battery is always in a low state of charge or an excessive amount of water must be added to the battery (more than one ounce of water per cell per week or per every 50 service hours).

When the alternator is either overcharging the battery or undercharging, the alternator charging rate can be adjusted. Remove the hollow head screw from the cover of the alternator regulator and use a screwdriver to turn the inside adjustment. Turn the adjustment toward the "+" to increase or toward the "-" to decrease the alternator charging rate.

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