Mechanical Inspection: Compression
Check engine mechanical condition with a compression gauge, vacuum gauge or engine analyzer. See engine analyzer manual for specific instructions.
WARNING:
DO NOT use ignition switch during compression tests on fuel injected vehicles. Crank engine with a remote starter. Fuel injectors on many models are triggered by ignition switch during cranking mode, which can create a fire hazard or contaminate the engine's oiling system.
COMPRESSION RATIO
| Application | Specification | |
|---|---|---|
| 2.5L | ||
| Cherokee & Comanche | 9.2:1 | |
| Wrangler | 9.1:1 | |
| 4.0L | 8.8:1 | |
NOTE:
Compression pressure and cylinder pressure variation are not available from manufacturer.