Mechanical Inspection: Compression

1992 Infiniti M30 2D ConvertibleSECTION Compression

Check engine mechanical condition using 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 engine oiling system.
COMPRESSION SPECIFICATIONS (1)

Application psi (kg/cm2 )
G20
Standard 178 (12.5)
Minimum 149 (10.2)
Maximum Differential 14 (1.0)
M30
Standard 173 (12.2)
Minimum 128 (9.0)
Maximum Differential 14 (1.0)
Q45
Standard 185 (13.0)
Minimum 142 (10.0)
Maximum Differential 14 (1.0)
(1) Readings taken at cranking speed (300 RPM).
RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.