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Home >> GMC >> 1991 >> Forward Control 5.7 K, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Fuel System (Diesel Glow Plug System Diagnosis) >> Preliminary Glow Plug Diagnosis

Preliminary Glow Plug Diagnosis

  1. If system does not operate as described in NORMAL GLOW PLUG CIRCUIT OPERATION, ensure glow plug system is correctly installed. Ensure all connectors are properly attached, clean and tight. Inspect engine harness ground connection. Ensure nut securing 4-wire connector at controller is tightened to 96 INCH lbs. (11 N.m), with connector fully seated and latched.
  2. Ensure controller copper stud upper nuts are tightened to 96 INCH lbs (11 N.m). DO NOT tighten lower nuts. Ensure temperature switch connector in water crossover near front of engine is tightened to 48 INCH lbs. (5.4 N.m). Inspect WAIT light on instrument panel for tight connection and operation.
NOTE: If all connections are intact, but glow plug system does not operate as stated, do the system diagnosis shown in Fig 1. Use this procedure whenever there is doubt about correct system operation. Then refer to diagnosis chart in Fig 2 to pinpoint condition.
Fig 1: Glow Plug Preliminary Diagnosis W/An Ammeter
G50G06627
Fig 2: Diesel Electrical System Diag. (1 of 2)
G50I06628
Fig 3: Diesel Electrical System Diag. (2 of 2)
G50A06629