Compression Check: Testing and Inspection

Engine Compression Test

Perform the following steps to conduct a compression test.

1. Conduct the following steps to check cylinder compression.
1. Engine should be at room temperature.
2. Disconnect wiring from the ignition module.
3. Remove the spark plugs.
4. Throttle body valve should be wide open.
5. Battery should be at or near full charge.
2. For each cylinder, crank engine through 4 compression strokes.
3. The lowest reading cylinder should not be less than 70 percent of the highest.
4. No cylinder reading should be less than 689 kPa (100 psi).

Important: The results of a compression test will fall into the following categories:

* Normal - Compression builds up quickly and evenly to specified compression on each cylinder.

* Piston rings - Compression is low on the first stroke, tends to build up on following strokes, but does not reach normal. Compression improves considerably with the addition of oil.

* Valves - Compression is low on the first stroke, does not tend to build up on the following strokes, and does not improve much with the addition of oil. Use approximately 3 squirts from a plunger-type oiler.