Glow Plug: Testing and Inspection

1986 Chevrolet G 20 Van V8-379 6.2L DSLSECTION Testing and Inspection

Glow Plug System Wiring Schematic:




Glow Plug System Diagnosis (Part 1 of 3):




Glow Plug System Diagnosis (Part 2 of 3):




Glow Plug System Diagnosis (Part 3 of 3):






CAUTION: The glow plug relays are automatically controlled. Do not attempt to bypass the relay terminals of the controller as the glow plugs will be damaged.

1. Inspect all system electrical connectors and ensure terminals are free from corrosion and that connectors are fully seated.
2. Inspect engine harness ground stud, ensuring wire end terminals are free from corrosion and that stud nut is properly tightened.
3. Inspect relay terminal lugs on controller, ensuring wire end terminals are free from corrosion and that nut are torqued to 3.9-5.1 Nm (35-45 in lbs).
4. If glow plugs function normally but glow plug lamp fails to light, inspect connections and bulb in instrument panel jumper harness and repair as needed.
5. If system fails to operate properly refer to wiring schematic and diagnostic charts.




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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.