Symptom Analysis

Consult the Symptom Analysis Diagnostic Procedures first. These will indicate a service to be performed or provide direction to either the Fast Start Glow Plug System Diagnostic Procedure or the Engine Performance Diagnostic Procedure.

If the GLOW PLUG lamp is suspected of being faulty, go directly to the GLOW PLUG 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 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 two categories according to the color of the smoke, blue-white and black.

The first category is 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 will also occur when the engine is operated at wide-open throttle (accelerator pedal to floor) 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 minimum to maximum 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:

- Heavy blue-white smoke.
- Fuel injection pump governor hunting resulting in high speed engine rpm surging.
- Engine sputtering or misfiring.

The conditions can be eliminated by not operating the engine above its maximum full load rated speed of 3300 rpm.

NOTE: Chassis fuel system air leaks may also cause continuous heavy blue-white smoke.

The second category of diesel exhaust smoke is 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.