Compression Check: Testing and Inspection

Perform the following steps in order to conduct a compression test:
1. Conduct the following steps in order to check cylinder compression:
a. Ensure engine is at room temperature.
b. Disconnect wiring from the ignition module.
c. Remove the spark plugs.
d. Throttle-body valve should be wide open.
e. Ensure battery should be at or near full charge.

2. For each-cylinder, crank engine through four compression strokes.
3. The lowest reading cylinder should not be less than 70% of the highest.
4. No cylinder reading should be less than 689 kPa (100 psi).

NOTE 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 low on first stroke. Tends to build up on following strokes but does not reach normal. Improves considerably with addition of oil.
^ Valves - Compression low on first stroke. Does not tend to build up on the following strokes. Does not improve much with addition of oil. Use approximately three squirts from a plunger-type oiler.