Compression Check: Testing and Inspection
MEASUREMENT OF COMPRESSION PRESSURE1. Warm up engine.
2. Turn ignition switch OFF.
3. Release fuel pressure.
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.