Compression Check

COMPRESSION CHECK Compression should not be less than 689 kPa (100 psi) and not vary more than 25 percent from cylinder to cylinder. Compression Pressure 1172 - 1551 kPa (170 - 225 psi)

COMPRESSION CHECK Compression should not be less than 689 kPa (100 psi) and not vary more than 25 percent from cylinder to cylinder. Compression Pressure 1172 - 1551 kPa (170 - 225 psi)

The combustion pressure leakage test provides an accurate means for determining engine condition.

Combustion pressure leakage testing will detect:

Exhaust and intake valve leaks (improper seating). Leaks between adjacent cylinders or into water jacket. Any causes for combustion/compression pressure loss.

1. Check the coolant level and fill as required. DO NOT install the radiator cap. 2. Start and operate the engine until it attains normal operating temperature, then turn the engine OFF. 3. Remove the spark plugs. 4. Remove the oil filler cap. 5. Remove the air cleaner. 6. Calibrate the tester according to the manufacturer's instructions. The shop air source for testing should maintain 483 kPa (70 psi) minimum, 1,379 kPa (200 psi) maximum and 552 kPa (80 psi) recommended. 7. Perform the test procedures on each cylinder according to the tester manufacturer's instructions. Set piston of cylinder to be tested at TDC compression. While testing, listen for pressurized air escaping through the throttle body, tailpipe and oil filler cap opening. Check for bubbles in the radiator coolant.

All gauge pressure indications should be equal, with no more than 25% leakage.

FOR EXAMPLE: At 552 kPa (80 psi) input pressure, a minimum of 414 kPa (60 psi) should be maintained in the cylinder.

The results of a cylinder compression pressure test can be utilized to diagnose several engine malfunctions.

Ensure the battery is completely charged and the engine starter motor is in good operating condition. Otherwise the indicated compression pressures may not be valid for diagnosis purposes.

1. Clean the spark plug recesses with compressed air. 2. Remove the spark plugs. 3. Secure the throttle in the wide-open position. 4. Disable the fuel system Refer to OPERATION . 5. Remove the ASD relay. Refer to REMOVAL . 6. Insert a compression pressure gauge and rotate the engine with the engine starter motor for three revolutions. 7. Record the compression pressure on the 3rd revolution. Continue the test for the remaining cylinders. 8. See SPECIFICATIONS for the correct engine compression pressures.

To determine if an engine cylinder head gasket is leaking between adjacent cylinders, follow the procedures in

Cylinder Compression Pressure Test. See CYLINDER COMPRESSION PRESSURE. An engine cylinder head gasket leaking between adjacent cylinders will result in approximately a 50 - 70% reduction in compression pressure.

With the engine cool, remove the coolant pressure cap. Start the engine and allow it to warm up until thermostat opens.

If a large combustion/compression pressure leak exists, bubbles will be visible in the coolant.

Combustion leaks into the cooling system can also be checked by using Bloc-Chek Kit C-3685-A or equivalent. Perform test following the procedures supplied with the tool kit.

To determine if an engine cylinder head gasket is leaking between adjacent cylinders, follow the procedures in Cylinder Compression Pressure Test. See CYLINDER COMPRESSION PRESSURE. An engine cylinder head gasket leaking between adjacent cylinders will result in approximately a 50 - 70% reduction in compression pressure.

With the engine cool, remove the coolant pressure cap. Start the engine and allow it to warm up until thermostat opens.

If a large combustion/compression pressure leak exists, bubbles will be visible in the coolant.

Combustion leaks into the cooling system can also be checked by using Bloc-Chek Kit C-3685-A or equivalent. Perform test following the procedures supplied with the tool kit.