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. Use a remote starter to crank engine. 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.
2.5L & 4.0L COMPRESSION RATIO
| Application | Specification | |
|---|---|---|
| Compression Ratio | ||
| 2.5L | 9.2:1 | |
| 4.0L | 8.8:1 | |
NOTE:
Compression pressure and cylinder pressure variation for 2.5L and 4.0L engines are not available from manufacturer.
5.9L COMPRESSION RATIO
| Application | Specification |
|---|---|
| Compression Ratio | 8.25:1 |
| Minimum Compression Pressure | 120 psi (8.4 kg/cm2 ) |
| Maximum Variation Between Cylinders | 30 psi (2.1 kg/cm2 ) |