Usage:
| NOTICE |
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The safe and reliable operation of all motor vehicles depends on proper service and repair procedures. The procedures recommended and described in this manual are effective methods for performing service operations. This manual contains information which should be followed to minimize the risk of personal injury to service personnel or damage to vehicles through unsafe service procedures. This information does not cover all the possible service hazards. Accordingly, anyone using a service procedure or tool not recommended must first be satisfied that their safety or the vehicle's safety will not be jeopardized by the method selected. |
General Description
The EL-740 Air Compressor is two cylinder, air or water cooled, and engine lubricated. It can be base or flange mounted.
The air compressor has a rated capacity of 7.4 CFM which is the displacement in cubic feet per minute (CFM) at 1250 rpm.
The EL-740 Air Compressor is designed with a ball-bearing at the front (the shaft end of the air compressor) and a sleeve-type rear bearing. Several models carry ball bearings front and rear. The air compressor is designed with a one-piece crankshaft.
Pistons are made of aluminum alloy. Each piston has three compression rings: one in the top groove, and two in the second groove (some older style air compressors have only two compression rings; one in each groove). In the groove below the wrist pin (the oil rail groove) is one expander ring and two oil rails. Thrust buttons are used on both ends of the wrist pin to retain the pin in the piston rod.
Rod bearings are replaceable insert type.
All valve components are installed within the head. The exhaust valves use a screw-in, spring-loaded, disc-type assembly located in the bottom of the head. The inlet valve guard and valve are pressed into the inlet cavity in the bottom of the head.
The unloader mechanism components are housed in the unloader assembly which is bolted to the top of the head. The unloader pins extend from the unloader assembly, through the cylinder head to the inlet valve cavity where they hold the inlet valves open when the air system is at maximum pressure.
Air Compressor Operation
During the down stroke of each piston, air is drawn into the cylinder bore through the inlet valve in the cylinder head. As each piston begins its upstroke, the inlet valve closes and the air above the piston is compressed.
When the pressure in the cylinder block becomes greater than the air pressure in the cylinder head above the exhaust valve, the exhaust valve is forced off the valve seat. Air passes through the exhaust port into the head cavity and into the air line leading to the air reservoir.
As the piston starts a down stroke, the exhaust valve returns to its seat. Compressed air is prevented from returning to the cylinder block, and the inlet and compression cycle is repeated.
Governor Operation
The governor, operating in conjunction with the air compressor unloader mechanism, automatically controls air pressure in the air system between the predetermined maximum and minimum pressures.
The air compressor runs continually while the engine operates, but air compression is controlled by the governor which stops and starts compression when the maximum or minimum pressure is reached.
Unloading (Not Compressing)
When air pressure in the system reaches the maximum governor pressure setting, the governor is actuated, allowing the system air pressure to actuate the unloader assembly causing the unloader pins to hold the inlet valves off their seats (open).
With the inlet valves open, air passes back and forth between the cylinder bores through the inlet cavity in the cylinder head to the inlet air cleaner eliminating the compression of air. When air pressure in the system is reduced to the governor cut-in setting, the governor reacts by exhausting the air pressure to the unloader assembly, thus releasing the unloader pins which allows the inlet valves to function normally permitting air compression.
Air Compressor Service Procedure
Air inlet filters should be cleaned or replaced when the vacuum level exceeds 1.2 kPa (20 inches of H2O) at compression. The governor settings and the unloader operation should be checked regularly. Maximum desirable reservoir pressure for highway brake use is 861 kPa (125 psi). Recommended pressure range is 103 to 207 kPa (15 to 30 psi).
Unloader components are serviced by removing the unloader assembly from the top of the air compressor head. Because of Midland's "valve-in-head" design, servicing the EL-740 Air Compressor for other than ring or bearing wear is accomplished by servicing or replacing the head assembly only. Inlet and exhaust valves are serviced in the same procedure.
Unloader
Exhaust Valve
Inlet Valve
If the cylinder head can not be rebuilt, replacement heads are available. The following replacement cylinder heads are available: Air Cooled-Threaded Port Type, Air Cooled-Manifold Type, Water Cooled-Threaded Port Type and Water Cooled-Manifold Type.
If an air compressor is in need of piston rings, bearings and seals, repair kits are available or a factory serviced air compressor can be installed. Pistons and rings are available in standard, 0.25 mm (.010 in) and 0.50 mm (.020 in) oversize. Bearing insert kits are available in standard, 0.25 mm (.010 in), 0.50 mm (.020 in) and 0.75 mm (.030 in) undersize.
NOTE:
1. Oversize cylinder blocks must be used in conjunction with oversize pistons.
2. Cylinder blocks that have been rebored oversize should be honed to ensure proper piston ring seating.
3. Air compressors that require new ring sets but do not require reboring of the cylinder block should have cylinder bores re-honed to a crosshatch pattern to ensure proper ring seating.
Air Compressor Disassembly
Mark the cylinder head, cylinder block and crankcase, as shown, to ensure the components are re-assembled correctly. EL-740 Air Compressors with a flanged inlet port on the block and a flanged exhaust port on the head must be reassembled with both ports on the same side of the air compressor.
Governor Assembly Removal
The governor may be mounted to the cylinder head, cylinder block or end cap by means of a bracket, or remote mounted.
Air Compressor Mounted Governor
1. Disconnect the unloader tube leading from the unloader assembly to the governor.
2. Disconnect the tube leading from the governor to the reservoir.
3. Remove the two bolts holding the governor to the mounting bracket.
NOTE: The bracket for a head mounted governor is removed when the cylinder head is removed from the cylinder block. The bracket for the cylinder block mounted governor is removed when the cylinder block is removed from the crankcase.
Remote Mounted Governors
1. Disconnect the unloader line.
2. Disconnect the line from the reservoir to the governor.
3. Remove the two bolts holding the governor to its mounting surface.
Air Cleaner Removal-Bolt-On Type
1. Remove the two bolts holding the air cleaner to the cylinder block.
2. Remove the air cleaner and discard the gasket. Clean the gasket surfaces. Do not damage the machined surfaces.
NOTE: Some air compressors do not have an air cleaner attached to the air compressor. These models are hose connected to the engine air cleaner. With this type application, the inlet (air) manifold should be removed from the cylinder block by removing the two bolts.
Air Cleaner Removal-Screw-In Type
Place a wrench on the nut mounted to the underside of the cleaner and loosen to remove. The air cleaner screws directly into the air compressor cylinder head.
Air Cleaner Inspection And Disassembly
1. Check the pressure drop across the air cleaner assembly. If the restriction is 1.2 kPa (20 inches of H2O) or greater the element should be replaced.
2. Examine the air cleaner cover. If bent, crushed or damaged replace with a new part.
3. Examine the filter body for cracks, damaged threads or defaced gasket surface. Replace, if necessary.
4. If the filter element is damaged it must be replaced.
NOTE: If filter element is removed from air cleaner assembly, the element should be discarded and replaced with a new part.
Air Cleaner Assembly
1. Reassemble the air cleaner assembly.
2. On air cleaner assemblies with a 4 5/16 inch diameter cover, the cover should be tightened 2/3 to 3/4 revolutions after the filter element seats on the cover and body. All remaining air cleaner assemblies have metal to metal contact, or have bolts and should be tightened accordingly.
Exhaust Manifold-Bolt-On Type
1. Remove the two bolts holding the exhaust manifold to the cylinder head.
2. Remove the exhaust manifold and discard the gasket. Remove all carbon, check for damaged threads and clean gasket surfaces. Do not damage machined surfaces.
NOTE: On air compressors without exhaust manifolds, remove the exhaust line from the cylinder head, and clean all carbon deposits from the line or replace the line.
Unloader Replacement
Unloader components can be replaced without removing the air compressor from the vehicle engine.
Unloader Removal
1. Reduce the air pressure in the reservoir to below 551 kPa (80 psi).
2. Remove the line from unloader to governor.
3. Remove two hex-headed bolts and lift the unloader assembly off the air compressor.
4. The unloader pins and springs will protrude from the cylinder head. Remove the pins from their bores.
5. Remove the unloader springs and discard.
Unloader Disassembly
Unloader
1. Remove bushings (6). (Some style unloader assemblies will have snap rings holding the bushings in place. A pair of snap ring pliers will be required to remove these retaining rings.)
2. Remove valve discs (4) and diaphragms (3) from the unloader body (1). Discard diaphragms (3) and expander springs (2).
Unloader Inspection
1. Examine the unloader body and bores for cracks, damaged threads, nicks or scratches. Replace as needed.
2. Check the unloader pins for damage. Measure the length of the pins. Pin bores must be within the limits stated in the "Specifications" section. If the pins are not within these limits they must be replaced.
Unloader Reassembly
1. Lubricate the bores in the unloader body with Dow-Corning #33 Lubricant.
2. Insert new expander springs into new diaphragm cups. Place the diaphragm cups into the bores of the unloader body with the expander springs facing the inside of the body.
3. Insert the valve discs and bushings into the unloader bores with the valve disc positioned next to the diaphragm cups.
NOTE: Some unloader assemblies use snap rings to retain the bushings in the unloader body. On this style assembly a pair of snap ring pliers will be required to install the snap rings.
Cylinder Head Removal
1. Remove the six bolts holding the cylinder head to the cylinder block.
2. Tap the cylinder head lightly with a brass or plastic hammer to loosen.
3. Lift the head assembly off the cylinder head.
4. Remove and discard the gasket. Clean the gasket surfaces. Do not damage the machined surfaces.
Cylinder Head Disassembly
1. Place the cylinder head in a soft-jawed vise, bottom side up.
2. Loosen the exhaust valve seats (9).
3. Unscrew and remove the exhaust valve seats (9), exhaust valve springs (17), washers (7), and exhaust valve cages (16).
4. Discard the exhaust valve springs, exhaust valves, and washers.
5. With a screwdriver carefully pry the inlet valve guards and pin assemblies (2) and inlet valves (3) from their cavities. Discard the inlet valves.
6. If the inlet valve guard is damaged during removal, replace with a new part.
NOTE: The inlet valve guards are prick punched to keep them in place during assembly. They are removed easily from their cavities.
Cylinder Block Removal
1. Remove the six nuts or cap screws and lock washers holding the cylinder block to the crankcase.
2. Tap the cylinder block lightly with a plastic or brass hammer to loosen, if necessary.
3. Pull the cylinder block off the crankshaft and pistons.
4. Remove and discard the gasket. Clean the gasket surfaces. Do not damage the machined surfaces.
Piston And Connecting Rod Removal
1. Place the air compressor on its side. On flange mounted air compressors, remove the bottom cover plate.
2. Mark the connecting rods and connecting rod caps to ensure they are returned to the same connecting rod from which they are removed.
3. Turn the crankshaft so that one connecting rod is at the bottom of its stroke.
4. Remove the connecting rod nuts.
5. Remove the connecting rod caps.
6. Lift the piston and connecting rod through the top of the crankcase.
7. Repeat Steps 2 through 6 on the remaining connecting rod.
NOTE: Each connecting rod cap must be installed on the same connecting rod from which it was removed.
Piston And Connecting Rod Disassembly
Piston Assembly
1. With a screwdriver remove the thrust buttons from the piston pins. On some EL-740 Air Compressors a wire pin is used in place of thrust buttons. The wire pin can be removed with a small screwdriver by prying the wire pin out of the retaining hole. Discard the wire pin. Replace it with thrust buttons.
2. Press the piston pin out of the piston and connecting rod assembly taking care not to damage the piston. The piston may be heated for ease of removal.
3. Remove the oil rings from the pistons using a piston ring expander, if necessary.
4. Discard all oil rings.
Crankshaft Bearing Cap Removal
1. Remove the four bolts securing the bearing cap (flange mount) or caps (base mount) to the crankcase.
2. Tap the bearing caps lightly to loosen. Do not attempt to pry the bearing caps off. Remove the bearing caps from the crankcase. Discard the gaskets. Clean the gasket surfaces. Do not damage the machined surfaces.
3. Remove the oil seal from the front bearing cap and discard.
4. On air compressors having rear ball bearings, remove the O-ring, when present, and discard.
5. On air compressors that are bottom oiled, remove the dumb-bell from between the crankcase and the rear bearing cap. Remove and discard the O-ring on the dumb-bell.
Crankshaft Removal
This manual does not include instructions for removing the crankshaft from the crankcase. If inspection shows the crankcase or crankshaft is damaged, the air compressor should be replaced with a new or remanufactured unit.
Air Compressor Inspection Procedure
Cleaning, Inspection And Repairing
1. Wash all parts in cleaning solvent. Blow dry all parts with compressed air.
2. Clean the carbon deposits from the interior surfaces of the cylinder head. Clean all interior air and water passageways.
3. Remove the carbon from the piston crowns and ring grooves. Carbon in ring grooves can be removed by using a piece of broken ring as a tool.
4. Blow out all drilled passageways with compressed air to ensure they are open.
5. Remove old gasket material sealer from the gasket surfaces.
Inspection - Cylinder Head And Components
NOTE: If component part measurements are not within the "Specifications" limits, the parts must be replaced.
1. Examine the cylinder head for cracks and damaged threads. All gasket surfaces and inlet valve surfaces must be free of nicks and gouges. Replace the cylinder head, if damaged.
2. Inspect the inlet and exhaust cavities for carbon deposits. Remove all carbon and clean the cavities.
3. Examine the exhaust valve seats for damage or wear. Measure the distance from the top of the valve seat to the valve seating surface. Dimensions must be within limits in the "Specifications" section. If the part is not within specified limits, discard and use a new part.
4. Examine the exhaust valve cages for damage or excessive wear.
A. Overall length. If parts are not within limits in the "Specifications" section, parts must be discarded and replaced with new parts.
B. Measure the distance from the tip (valve end) of the exhaust valve cage to the surface where the spring sets (this distance is to include any wear caused by the spring). If parts are not within limits in the "Specifications" section, parts must be discarded and replaced.
5. Examine the inlet valve guard for nicks, burrs or deformed parts. Damaged parts must be replaced.
Pistons, Connecting Rods And Bearings
1. Examine the pistons for scoring, nicks, burrs, cracks, or other damage. Replace, as needed.
2. Measure the outside diameter of the piston at a 90 degree angle to the piston pin bore. Compare this measurement with the diameter of the cylinder bore. Piston to cylinder bore clearance should not exceed 0.20 mm (.008 in). If clearance exceeds 0.20 mm (.008 in), replace the pistons. The cylinder block must be replaced or bored oversize 0.25 mm (.010 in) or 0.50 mm (.020 in). Oversize pistons 0.25 mm (.010 in) or 0.50 mm (.020 in) and oversize piston ring sets are available.
NOTE: Oversize pistons and rings must be used in conjunction with oversize cylinder bores. When measuring the outside diameter of the piston the micrometer must be at a 90 degree angle to the piston pin bore. This will permit a correct measurement.
3. Check the fit of the piston pin in the piston and connecting rod. The piston pin must have a light interference fit in the piston and a slip fit in the connecting rod. Determine which part or parts are worn and replace as required. The connecting rod and connecting rod cap must be replaced as a unit.
4. Check the fit of the compression and oil rings in the piston ring grooves. The oil rings must move freely on the piston. Place the oil rings in the cylinder bores and measure the ring gap. If the ring gaps are not within the limits of the "Specifications" section, new oil rings must be installed.
NOTE: When new oil rings are used, cylinder bores should be re-honed.
5. Examine the connecting rod bearing inserts for scoring, pitting or visible wear. Check the fit of the connecting rod bearings on the crankshaft journals. Clearance between the rod bearings and the crankshaft journal must be between 0.013 mm (.0005 in) and 0.053 mm (.0021 in). If damage is evident or clearance does not meet the specified dimensions, new rod bearing inserts must be installed.
6. Check the clearance between the side of the connecting rod and the crankshaft. If clearance exceeds 0.254 mm (.0100 in), a new connecting rod assembly must be installed.
NOTE: The connecting rod and connecting rod cap must be replaced as a unit.
Cylinder Block
1. Examine the cylinder block for cracks. Replace, if damaged.
2. Examine the cylinder bores for scratches, scoring and pitting. Check the cylinder bores for out-of-round or taper. If out-of-round more than 0.013 mm (.0005 in), or tapered more than 0.025 mm (.0010 in) from top to bottom of bore, or scratched, scored, or pitted, the cylinder block must be re-bored or honed oversize, or replaced with a new cylinder block. Service pistons are available at 0.25 mm (.010 in) and 0.50 mm (.020 in) oversize.
Crankshaft And Bearings
1. A bent or twisted crankshaft cannot be repaired. If the connecting rod journals are scored beyond repair or worn beyond the limits in the "Specifications" section, replace with a new crankshaft or regrind the connecting rod journals. Service insert bearings are available at 0.25, 0.50 and 0.75 mm (.010, .020 and .030 in) undersize.
2. If the main bearing journal on an air compressor, which has a sleeve main bearing, is scored excessively or worn beyond the limits of the "Specifications" section, it must be replaced. No undersize bearings are available.
3. Keyway, threads and all ground and machined surfaces must not be damaged or worn.
4. Crankshaft oil passages must be cleaned to ensure oil flow.
5. Examine the ball bearings for worn or damaged balls; rotate the ball bearing by hand to detect roughness. If wear, roughness or damage is evident, the ball bearing must be replaced.
Crankshaft Bearing Caps
1. Examine front and rear bearing caps (base mount). Replace if cracked, or if the gasket surfaces have been defaced.
2. On air compressors with a sleeve-type rear bearing, check the inside diameter of the rear bearing. If the dimensional limits of the rear bearings exceed the limits stated in the "Specifications" section or is damaged, the bearing cap must be replaced.
Crankcase
1. Examine the crankcase for cracks and damage to the gasket surfaces. Replace, if necessary.
2. Inspect the studs in the crankcase, if used. Replace any bent or damaged studs.
3. On bottom lubricated crankcases the oil passage must be thoroughly cleaned to ensure oil flow.
4. Clean all gasket surfaces. Ensure that all gasket surfaces are free of nicks, scratches and burrs that would affect a good gasket seal. Replace, as required.
Air Compressor Assembly
Before reassembly, put engine oil on the crankshaft, bearings, connecting rod bearings, pistons, pins and cylinder bores.
NOTE: Special parts, in addition to standard parts, are available for overhauling each air compressor. Included are: 0.25 and 0.50 mm (.010 and .020 in) oversize pistons and rings, cylinder blocks with 0.25 and 0.50 mm (.010 and .020 in) inch oversize cylinder bores, and 0.25, 0.50 and 0.75 mm (.010, .020 and .030 in) undersize bearing inserts. Refer to the "Specifications" section.
Crankshaft Bearing Installation
1. Press a new oil seal into the front bearing cap. Use a sealer on the outer rim of the oil seal. The spring side of the oil seal must face the crankcase when installed. The seal case should be flush to 0.15 mm (.006 in) below the front surface of the bearing cap.
2. Place a new gasket on the crankcase cap mating surface.
3. Apply a small amount of engine oil to the lip of the oil seal. Slide the front bearing cap over the crankshaft end. Do not damage the oil seal.
4. Install the four bearing cap bolts torquing alternately to 13 to 18 N·m (120 to 160 lb ft).
5. Place a new gasket on the rear bearing cap.
6. On air compressors with sleeve-type bearings, slide the rear bearing cap over the crankshaft end. Align the crankshaft and bearing cap so that the bearing cap fits evenly in the crankcase bore.
7. On air compressors with rear ball bearings, slide the rear bearing cap over the ball bearing.
8. Install the four bearing cap bolts torquing alternately to 13 to 18 N·m (120 to 160 lb ft).
9. Ensure the crankshaft turns freely after installing the bearing caps.
10. On air compressors that are bottom oiled, place two new O-rings on the dumb-bell. (Lubricate the dumb-bell with a film of engine oil before assembly). Insert the dumb-bell into the rear of the crankcase and proceed with Step 5 above.
Assembly Of Pistons And Connecting Rods
1. Lubricate the piston pin, piston pin bores and piston pin diameters in the connecting rod with engine oil.
2. Position the connecting rod in the piston and press the piston pin into place.
3. Install thrust buttons into the piston pin ends.
4. Install compression rings in the two top grooves of the piston.
NOTE: Some pistons will require two compression rings; one in each of the two top grooves. Other pistons will require three compression rings; one in the top groove and two in the second or middle groove. Compression rings must be installed with surface marked "Top" facing top of the piston. Some compression rings may have dots indicating the top of the ring.
5. Install the expander ring and two oil rails in the bottom groove of the piston.
6. Press the connecting rod bearing inserts into the connecting rod and bearing cap. Ensure the locating lips on the bearing inserts engage the locking notches in the connecting rod and bearing cap. Ensure each connecting rod cap is installed on the connecting rod from which it was removed.
7. Lubricate with engine oil the connecting rod bearings.
Assembly Of Piston And Connecting Rod To Crankshaft
1. Place the crankcase and crankshaft assembly on its side.
2. Remove the bearing cap and insert the assembly from the piston and connecting rod assembly.
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Care should be taken to ensure each connecting rod and connecting rod cap are always kept in the same pairing - DO NOT intermix connecting rods and connecting rod caps. |
3. Lubricate with engine oil the bearing inserts on the connecting rods and connecting rod caps, and the connecting rod journals on the crankshaft.
4. Ensure the bearing inserts are in proper position on their respective connecting rod; assemble the connecting rod and piston assembly to the crankshaft through the top of the crankcase.
5. Install the connecting rod bearing cap and insert to connecting rod. Refer to the "Notice" under Paragraph 2.
6. Install the connecting rod nuts and tighten to a torque of 11 to 16 N·m (100 to 140 lb in).
7. Assemble the second piston and connecting rod assembly using the same procedure.
8. Ensure that each connecting rod assembly moves freely on the crankshaft.
Assembly Of Cylinder Block To Crankcase
1. Position the crankcase so that the pistons are pointing up. On flange mounted air compressors it may be advisable to place the crankcase in a soft-jawed vise.
2. Lubricate the cylinder block bores, pistons, and piston rings with lubricating oil.
3. Place a new gasket on the crankcase.
4. Rotate the crankshaft so that the piston and connecting rod assemblies are at the top center and bottom center, respectively.
5. Recheck the ring position gaps.
6. On cylinder blocks having an inlet mounting pad surface, rotate the cylinder block with respect to the crankshaft to ensure proper location of the air cleaner assembly.
7. Place the cylinder block over the pistons. Slowly bring the cylinder block down onto the pistons until the cylinder block is flush to the crankcase.
NOTE: A slight downward pressure will be required to move the cylinder block down as it will be squeezing the piston rings when they slide into their respective bores.
8. If the governor bracket was mounted to the cylinder block before disassembly, replace the governor bracket in its original position.
9. Assemble the six cap screws or nuts, and lock washers. Torque the two center bolts from 7 to 9 N·m (60 to 80 lb in); then the four end bolts. Increase the bolt torque from 13 to 18 N·m (120 to 160 lb ft) tightening the two center bolts and then the four end bolts.
Assembly Of Cylinder Head
1. Place the cylinder head, bottom side up in a soft-jawed vise.
2. Insert the exhaust valve cages into the exhaust cavities. (Use new parts, if necessary. Refer to the "Specifications" section.)
3. Place new exhaust valve springs on the exhaust valve cages.
4. Place new copper washers into the exhaust cavities.
5. Place new exhaust valve on the exhaust valve spring.
6. Assemble the exhaust valve seats. (Use new parts, if necessary. Refer to the "Specifications" section.)
7. Tighten the exhaust valve seats to a torque of 70 to 90 N·m (52 to 67 lb ft).
8. Place a new inlet valve over the pin on the inlet valve guard. (Replace the inlet valve guard, if damaged.) Place the valve and guard assembly into the inlet cavity of the cylinder head.
9. Prick-punch the valve guard into the cylinder head to keep the valve and guard assembly from falling out during installation of the cylinder head to the cylinder block.
NOTE: The inlet valve guard should not protrude more than 0.18 mm (.007 in) above the surface of the cylinder head.
Installation Of Cylinder Head To Cylinder Block
1. Place new head to block gasket on cylinder block.
2. With cylinder head rotated to the proper position (to ensure proper porting); place the cylinder head onto the cylinder block.
3. If the governor bracket was mounted on the cylinder head before disassembly, replace the governor bracket to its proper position at this time.
4. Assemble the six bolts. Tighten the two center bolts to a torque of 14 to 18 N·m (125 to 160 lb in), then the four end bolts. Increase the bolt torque to 21 to 28 N·m (185 to 245 lb in). Torque the two center bolts first and then the four end bolts.
Air Compressor Assembly
There are two bottom plates available with the EL-740 Air Compressor: an eight bolt and a ten bolt design.
Bottom Plate Installation (Flange Type)
The eight bolt design should be tightened in numerical sequence to a torque of 11 to 17 N·m (100 to 150 lb in).
Bottom Plate Installation (Flange Type)
The ten bolt design should be tightened in numerical sequence to a torque of 8 to 12 N·m (75 to 105 lb in).
Installation Of Governor
1. Mount the governor to the cylinder head or block bracket.
2. Using two 5/16-18 bolts with lock washers, tighten the nuts to a torque of 12 to 17 N·m (110 to 150 lb in).
3. Replace the tube between the unloader assembly and governor. Tighten securely.
NOTE: On remote mounted governors, omit Steps 1 and 2.
Air Compressor Assembly
Installation of Base Mounted Air Compressors
Base mounted air compressors should be bolted to the engine block and bolts tightened in numerical sequence to a torque of 8 to 12 N·m (75 to 105 lb in).
Air Compressor Testing
Install a governor assembly to the air compressor, if one has not been installed previously. Connect an oil supply line having at least 138 kPa (20 psi) of oil pressure at the rear bearing cap. Provisions must be made for unrestricted oil drainage from the crankcase during the test. The oil return line must be 1/2 inch I.D. minimum.
If water-cooled, connect a water supply line which will permit a flow of 5.7 L (1.5 gal U.S.) of water per minute at the air compressor.
Connect the discharge port to an air tank with a known volume of 1/2 inch O.D. copper line or equivalent. The tank should have a quick-opening valve to exhaust air pressure. Connect a line from the air tank to the reservoir port to the governor.
If tests are being made in a dusty atmosphere, connect a suitable air cleaner to the air compressor air inlet opening. Connect the air compressor to a source of power (at least two horsepower) to run at 1250 rpm.
Run the air compressor at 1250 rpm pumping against a 689 kPa (100 psi) pressure for five minutes. This time should be used to adjust and test the governor. During this test, check for oil and air leakage, overheating and excessive noise. Decrease the pressure in the air tank to 0 kPa (0 psi). Close the quick-opening valve and check the build-up time from 0 to 689 kPa (0 to 100 psi) in the air tank.
The build-up time must not exceed 55.0 seconds per 100 cubic inches of tank volume for the EL-740 Air Compressor.
To determine the allowable build-up time, use the following formula:
EL-740 Air Compressor allowable build-up time (seconds) = air tank volume (cubic inches) × 0.055.
NOTE: If the air compressor is belt driven and the pulley is removed during the overhaul, it must be replaced with the same size pulley. A different size pulley will require a different size drive belt. Also, the air compressor output will change in relation to the engine rpm.
Troubleshooting
- 1. Air Compressor Fails To Maintain Sufficient Pressure Or Adequate Air.
- 2. Noisy Operation.
- 3. Air Compressor Passes Excessive Oil.
- 4. Air Compressor Not Unloading (excessive pressure).
- 2. Noisy Operation.
Troubleshooting Problems
Problem 1: Air Compressor Fails To Maintain Sufficient Pressure Or Adequate Air
Possible Causes:
- 1. Dirty Inlet Cleaner.
- 2. Restriction In Air Compressor Cylinder Head Inlet, Discharge Cavities Or Line.
- 3. Leaking Or Broken Inlet Or Exhaust Valves.
- 4. Excessive Wear.
- 5. Drive Belt Slipping.
- 6. Excessive System Leakage Or Usage.
- 7. Defective Governor.
- 8. Worn Unloader Seals.
- 9. Governor Setting Incorrect.
- 10. Gauge Defective.
- 2. Restriction In Air Compressor Cylinder Head Inlet, Discharge Cavities Or Line.
Problem 2: Noisy Operation
Possible Causes:
- 1. Loose Drive Pulley.
- 2. Restriction In Cylinder Head Or Discharge Line.
- 3. Worn Or Burned Out Bearings.
- 4. Air Compressor Not Receiving Proper Lubrication.
- 5. Excessive Wear.
- 2. Restriction In Cylinder Head Or Discharge Line.
Problem 3: Air Compressor Passes Excessive Oil
Possible Causes:
- 1. Excessive Wear.
- 2. Dirty Air Cleaner (improper air cleaner maintenance).
- 3. High Inlet Vacuum.
- 4. Small Or Restricted Oil Return Line Flooding Air Compressor.
- 5. Piston Rings Not Properly Installed.
- 6. Back Pressure From Engine Crankcase.
- 7. Inlet Pipe Restricted - Too Small Or Too Long.
- 8. Excessive Oil Pressure.
- 2. Dirty Air Cleaner (improper air cleaner maintenance).
Problem 4: Air Compressor Not Unloading (excessive pressure)
Possible Causes:
- 1. Defective Unloader Pins Or Seals.
- 2. Defective Governor.
- 3. Reservoir Line To Governor Restricted.
- 4. Unloader Mechanism Binding Or Stuck.
- 5. Gauge Defective.
- 2. Defective Governor.
Specifications
EL-740 Air Compressor
- Type - Two cylinder
- Rating - 7.4 cubic feet per minute
Cylinder Head Components
- Exhaust valve seat top of valve seat to seating surface - 3.18 to 3.25 mm (.125 to .128 in)
Exhaust Valve Cage:
- Overall length - 22.66 to 22.76 mm (.892 to .896 in)
- Valve stop surface to spring seat surface - 18.29 to 18.80 mm (.720 to .740 in)
Piston And Connecting Rod Components
Pistons:
- Piston diameter (standard) - 50.66 to 50.69 mm (1.995 to 1.996 in)
- Piston diameter 0.25 mm (.010 oversize) - 50.91 to 50.94 mm (2.005 to 2.006 in)
- Piston diameter 0.50 mm (.020 oversize) - 51.17 to 51.19 mm (2.015 to 2.016 in)
- Piston pin hole diameter - 12.586 to 12.695 mm (.4955 to .4998 in)
- Piston diameter 0.25 mm (.010 oversize) - 50.91 to 50.94 mm (2.005 to 2.006 in)
Connecting Rod:
- Piston pin hole diameter - 12.705 to 12.710 mm (.5002 to .5004 in)
Piston Pin:
- Piston pin diameter - 12.695 to 12.700 mm (.4998 to .5000 in)
Piston Rings:
- Compression ring gap in 2.000 inch bore - 0.127 to 0.254 mm (.0050 to .0100 in)
- Oil ring gap in 2.000 inch bore - 0.254 to 1.016 mm (.0100 to .0400 in)
Groove to ring clearance:
- Air Compressor rings - 0.127 to 0.762 mm (.0050 to .0300 in)
- Oil rings - 0.0127 to 0.1270 mm (.00050 to .00500 in)
Cylinder Block
- Cylinder bore diameter (Standard) - 50.787 to 50.800 mm (1.9995 to 2.0000 in)
- Cylinder bore diameter 0.25 mm (.010 Oversize) - 51.041 to 51.054 mm (2.0095 to 2.0100 in)
- Cylinder bore diameter 0.50 mm (.020 Oversize) - 51.295 to 51.308 mm (2.0195 to 2.0200 in)
- Cylinder bore diameter 0.25 mm (.010 Oversize) - 51.041 to 51.054 mm (2.0095 to 2.0100 in)
Crankshaft
- Connecting Rod Journal Diameter:
- Standard - 28.524 to 28.537 mm (1.1230 to 1.1235 in)
- 0.25 mm (.010 in) Undersize - 28.270 to 28.283 mm (1.1130 to 1.1135 in)
- 0.50 mm (.020 in) Undersize - 28.016 to 28.029 mm (1.1030 to 1.1035 in)
- 0.75 mm (.030 in) Undersize - 27.762 to 27.775 mm (1.0930 to 1.0935 in)
- 0.25 mm (.010 in) Undersize - 28.270 to 28.283 mm (1.1130 to 1.1135 in)
- Connecting rod journal width - 25.40 to 25.451 mm (1.000 to 1.002 in)
- Main bearing journal diameter - 34.999 to 35.011 mm (1.3779 to 1.3784 in)
Air Compressor Governor
- Cut-out pressure setting - 827 to 861 kPa (120 to 125 psi)
- Cut-in pressure setting - 710 to 737 kpa (103 to 107 psi)
Crankcase
Bearing Bore Diameters:
- Cast Iron - 71.99 to 72.01 mm (2.834 to 2.835 in)
- Aluminum - 71.96 to 71.98 mm (2.833 to 2.834 in)
Bearing Cap
- Bearing Bore Diameter - 35.04 to 35.08 mm (1.380 to 1.381 in)
Ball Bearing
- Outside Diameter - 71.99 to 72.00 mm (2.834 to 2.835 in)
- Inside Diameter - 34.99 to 35.00 mm (1.378 to 1.378 in)
Unloader Pin
- Pin Length - 32.51 to 32.77 mm (1.280 to 1.290 in)
- Pin Length - 48.64 to 48.90 mm (1.915 to 1.925 in)
- Pin Length - 54.18 to 54.43 mm (2.133 to 2.143 in)
- Pin Length - 48.64 to 48.90 mm (1.915 to 1.925 in)
NOTE: Pin length required is determined by the combination of cylinder head and unloader assembly used.