Symptom Related Diagnostic Procedures

TESTING NOTES
- Consult the diagnostic charts first. These will indicate a service to be performed or provide direction to the appropriate pinpoint test.
- If the glow plug indicator is suspected of being faulty, go directly to the glow plug indicator diagnostic procedure before performing the glow plug system diagnostic procedure.
- If the problem is loss of power and/or increased fuel consumption, go directly to the engine performance diagnostic procedure.

EVALUATING NORMAL DIESEL ENGINE EXHAUST SMOKE
The following is a description of what is normal and expected exhaust smoke for a vehicle with a diesel engine. Diesel exhaust smoke can be classified into categories according to the color of the smoke.

Blue-white Smoke
- Blue-white smoke may be observed at engine start-up whether the engine is up to operating temperatures or not. This start-up smoke will be observed at all ambient temperatures and should last no longer than a minute after the vehicle is driven.
- When ambient temperature is below 10°C (50°F), blue-white smoke can return after the engine warm-up due to extended idling. This is due to the combustion chambers cooling down during periods of extended idling time.

Heavy Blue-White Smoke.
- Heavy blue-white smoke will occur when the engine is operated at wide-open throttle with the transmission in neutral or with a lightly loaded vehicle in any transmission gear setting. The smoke is a normal characteristic for a diesel engine with a light governor spring in the fuel injection pump. This results in the following characteristics due to the engine operating above its rated speed (3300 rpm) in a no-load or lightly loaded condition:
- Fuel injection pump governor hunting resulting in high speed engine rpm surging.
- Engine sputtering or misfiring.
- Chassis fuel system air leaks may also cause continuous heavy blue-white smoke.

Black Smoke
- Black smoke occurs whenever the engine is working hard. The engine works hard when it is going up a steep grade, pulling a trailer, carrying a heavy load, or during acceleration.
- More black smoke will be observed when operating the vehicle at higher altitudes.
- If black smoke is observed while the engine is idling (at low altitude) or under normal driving conditions, the problem should be diagnosed as soon as possible.