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Home >> GMC >> 1998 >> Forward Control 7.4 J >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Basic Diagnostic Procedures - 7.4L >> Preliminary Inspection & Adjustments >> Mechanical Inspection >> Compression
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Mechanical Inspection: Compression

Check engine mechanical condition with a compression gauge, vacuum gauge, or an engine analyzer. See engine analyzer manual for specific instructions. For compression specifications, see SPECIFICATIONS - 7.4L article.

WARNING: Because fuel injectors on many models are triggered by ignition switch during cranking mode, DO NOT use ignition switch during compression tests. Use a remote starter to crank engine to prevent fire hazard or engine's oiling system contamination.
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