Mechanical Inspection: Compression
Check engine mechanical condition with compression gauge, vacuum gauge, or engine analyzer. See engine analyzer instruction manual for specific instructions.
CAUTION:
Use a remote starter to crank engine during compression test. DO NOT use ignition switch. Fuel injectors on many fuel-injected models are triggered during cranking mode. This could cause a fire hazard, flooding, crankcase contamination, hydrostatic lock, or lubrication to be washed off cylinder walls.
Measure engine compression at normal operating temperature with all spark plugs removed. To prevent damage to catalytic converter, test quickly and only if necessary.
NOTE:
Compression pressures are not specified by manufacturer. However, maximum variation between cylinders should not exceed 29 psi.
COMPRESSION RATIO
| Application | Specification | |
|---|---|---|
| 9-3 Series | ||
| 2.0L | 9.2:1 | |
| 2.3L | 9.35:1 | |
| 9-5 Series | ||
| 2.3L | 9.35:1 | |
| 3.0L | 9.5:1 | |