GM 6.5L V8 – Diagnosis – Condition Verification

The process of verifying that a condition related to a component of the 6.5L V8 turbo diesel engine exists includes the following steps:

1. Inspect the level and condition of fluids, and observe any leakage from components:
– Engine oil
– Coolant
– Fuel

2. Inspect the condition and tension of the accessory drive belt.

3. Inspect the condition of the outside air intake and air filter element.

4. Inspect electrical wiring and connectors:
– Left battery
– Right battery
– Generator
– Cranking motor
– Fuel shut-off solenoid
– Housing Pressure Cold Advance solenoid
– Fast idle solenoid
– Throttle Position Sensor
– Engine speed sensor
– Water In Fuel sensor
– Fuel heater
– Oil pressure switch/sending unit
– Glow plug controller/relay
– Glow plugs

5. Inspect electrical wiring and connectors (continued):
– Block heater
– Coolant temperature switch/sending unit
– Low coolant probe
– Fuel pump relay
– Junction block and fusible links
– Fuses
– Fuel pump

6. Operate the engine (if possible) and observe the following:
– Check the basic function of the glow plug, cranking, charging and fast idle/cold advance systems.
– Listen for unusual noises.
– Look for excessive exhaust smoke.
– Observe the smoothness of engine operation at various speeds.

7. Operate the vehicle (if possible) and observe the following:
– Listen for unusual noises.
– Look for excessive exhaust smoke.
– Observe the smoothness of engine, transmission and driveline operation at various vehicle speeds
and loads.

Based on these initial checks, do one of three things:
• If a condition is not found, consult the service advisor, vehicle owner or operator for more diagnostic
• If both a condition and its cause are found, make a repair and verify it.
• If a condition (but no cause) is found, proceed to the next section, Identifying a Condition.


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