Compression Test

1. Conduct the following steps in order to check cylinder compression:
   • Engine should be at room temperature.
   • Disconnect wiring from ignition module.
   • Remove spark plugs.
   • Throttle body valve should be wide open.
   • Battery should be at or about 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 reading.
4. No cylinder reading should be less than 100 psi (689 kPa)

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 about 3 squirts from a plunger-type oiler.