Compression Check: Testing and Inspection
MEASUREMENT OF COMPRESSION PRESSURE1. Warm up engine.
2. Turn ignition switch OFF.
3. Release fuel pressure.
Refer to Powertrain Management; Fuel Delivery and Air Induction; Fuel Pressure Release.
4. Disconnect ignition coil with power transistor harness connectors, then remove ignition coils.
5. Remove all spark plugs.
6. Remove fuse for fuel injector.
7. Attach a compression tester to No. 1 cylinder.
8. Depress accelerator pedal fully to keep throttle valve wide open.
9. Crank engine and record highest gauge indication.
10. Repeat the measurement on each cylinder as shown above.
^ Always use a fully-charged battery to obtain specified engine speed.
11. If compression in one or more cylinders is low:
a. Pour a small amount of engine oil into cylinders through spark plug holes.
b. Retest compression.
^ If adding oil helps compression, piston rings may be worn or damaged. If so, replace piston rings after checking piston.
^ If pressure stays low, a valve may be sticking or seating improperly. Inspect and repair valve and valve seat.
If valve or valve seat is damaged excessively, replace them.
^ If compression stays low in two cylinders that are next to each other:
a) The cylinder head gasket may be leaking, or
b) Both cylinders may have valve component damage. Inspect and repair as necessary.