How to do a compression test on your engine
Measurement of Compression Pressure
1. Warm up engine.
2. Turn ignition switch off.
3. Release fuel pressure (See How to Change Fuel Filter)
4. Remove all spark plugs.
5. Disconnect distributor center cable.
6. Attach a compression tester to No. 1 cylinder.
7. Depress accelerator pedal fully to keep throttle valve wide open.
8. Crank engine (let it turn over 7 times) and record highest gauge indication.
9. Repeat the measurement on each cylinder as shown above.
Note: Always use a fully charged battery to obtain specific engine revolution.
Compression Pressure kPa (kg/cm2, psi) / RPM
Standard = 1,236 (12.6, 179) / 300
Minimum = 1,040 (10.6, 151) / 300
Difference limit between cylinders = 98 (1.0, 14) / 300
10. If cylinder compression in one or more cylinders is low, pour a small amount of engine oil into the cylinders through the spark plug hole and re-test 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 compression in any two adjacent cylinders is low and if oil does not help compression, there is a leak past the gasket surface. If so, replace cylinder head gasket.
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