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.