Mechanical Inspection: Compression

1991 Saab 900 Base, 2D Convertible, AutomaticSECTION Compression

Check engine mechanical condition with a compression gauge, vacuum gauge, or an engine analyzer. See engine analyzer instruction manual for specific instructions.

CAUTION: Use a remote starter to crank engine during compression test, NOT the ignition switch. The fuel injectors on many fuel injected models are triggered during the cranking mode. This could cause a fire hazard, flooding, crankcase contamination, hydrostatic lock, or lubrication to be washed off of cylinder walls.

Check engine compression at normal operating temperature with all spark plugs removed. To prevent damage to catalytic converter, make tests quickly and only when necessary.

ENGINE COMPRESSION (1)

Application Specification
Compression Ratio
900 Non-Turbo 10.1:1
900 Turbo 9.0:1
9000 Non-Turbo 10.1:1
9000 Turbo 8.5:1
(1)
Compression pressure is not specified by manufacturer.
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:

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