Mechanical Inspection: Compression
Check engine mechanical condition using a compression gauge, vacuum gauge or engine analyzer. If using engine analyzer, see engine analyzer manual for specific instructions. On all models except Villager, compression pressures are considered within specifications if lowest reading cylinder is within 75 percent of highest reading cylinder. On Villager, compression should be 173 psi (1193 kPa). Minimum compression should be 128 psi (883 kPa). Maximum compression variation allowed between cylinders is 14 psi (97 kPa).
WARNING:
Because fuel injectors on many models are triggered by the ignition switch, DO NOT use ignition switch during compression tests on fuel injected vehicles. Use a remote starter to crank engine to prevent fire hazard or engine oiling system contamination.