Compression Pressure

CAUTION: Always remove the DME engine control master relay so that ignition coils will not be energized during compression pressure test.

Compression pressure should be checked at major service intervals and whenever engine mechanical condition is suspected as the cause of a driveability or emissions related malfunction. Check compression pressures as follows:

1. Ensure battery is fully charged. Engine must rotate at normal cranking speed during test.
2. Run engine until normal operating temperature is reached, then stop engine.
3. Remove spark plugs and secure throttle plate in wide open position.
4. Remove main or starting fuel pump relay, then disable ignition system by disconnecting electrical connector to control unit.
5. Check compression for each cylinder using suitable gauge, record readings.
6. Correct compression pressure specification is 143-156 psi. Maximum deviation between any two cylinders is 7 psi.