1978/03/13 Caterpillar

1100 and 3100 Series Engines, 3208 Engines In All Applications

During cold starts, diesel engines will generally show some white exhaust smoke. Some white smoke is a normal condition and is not an indication of a mechanical failure. But, the amount of white exhaust smoke and its duration (time during which smoke is present) can some times cause complaints. The information that follows will permit you to determine (find) the causes for white exhaust smoke, and which of the maintenance aids is most acceptable to your needs.

Characteristics of White Exhaust Smoke

White exhaust smoke is made up of fuel vapors and aldehydes which are the result of fuel that is not completely burned during combustion. An ignition delay is often the cause for the incomplete (not complete) combustion. The ignition delay is the result of not enough heat within the engine to cause the fuel to burn at the correct time.

Abnormal and Normal White Exhaust Smoke

Ambient (outside) and engine temperatures are a major part of this condition. The temperatures given below are examples and some adjustments will have to be made in your analysis of your engine's condition.

At an ambient and engine temperature of 15°F (-9°C), white exhaust smoke can generally be seen for approximately 8 to 16 minutes with the engine at 1400 rpm idle speed. Lower ambient temperatures will increase the amount and duration of the white exhaust smoke. To decrease the duration, put a load on the engine. This increases the engine temperature more quickly for better combustion.

If the duration of white exhaust smoke is more than 20 minutes at 1400 rpm and the ambient and engine temperature is 15°F (-9°C), this is an abnormal condition. The engine must be checked for correct operation, and the fuel must be checked for low API gravity and/or cetane number.

If the duration of white exhaust smoke is 8 to 10 minutes at low idle and the ambient and engine temperature is 15°F (-9°C), you can either follow the same procedure for an abnormal condition or use one or more of the maintenance aids to improve the condition.

Troubleshooting the Abnormal Condition

If the white exhaust smoke is abnormal or not acceptable, work can be done to the basic engine or changes made to the fuel to decrease the amount and duration of white exhaust smoke.

1. Check the fuel quality, A.P.I. gravity and cetane number.

NOTE: See your fuel supplier to get the cetane number.

Use a light diesel fuel or kerosene in the A.P.I. range of 41-44. The minimum cetane number for direct injection engines is 40. Fuels with these recommendations will cause less white exhaust smoke, improve the ability for the engine to start and to operate smoothly.

NOTE: See Special Instruction Form No. SEHS7067, "Fuels for Caterpillar Diesel Engines" for a list of fuel recommendations.

2. Check the fuel system timing. Make sure the timing is not retarded (slow). To get the best accuracy, use the fuel flow timing method. Put the setting at the high limit of 17°. The specification for 3208 Engines is 16° ± 1°. Use Special Instruction Form No. FM035709-08.

3. Check for air in the fuel system. Use Special Instruction Form No. GMG00825-01, "Observing Fuel Flow To Check For Excessive Air In Fuel Systems" and the information found in the April 26, 1976 Service Magazine "Air In Sleeve Metering Fuel Systems".

Maintenance Aids

If the white exhaust smoke is still not acceptable after the troubleshooting, three maintenance aids are available to decrease the smoke condition. These are as follows:

1. 9N3829 Jacket Water Heater Group. This group has two 1000 Watt, 120V heater elements, one for each side of the engine, to heat the coolant in the cylinder block. This increases the combustion compression temperature so the fuel will burn more completely. For engines that are equipped with sound suppression panels, some modification must be made to a panel on each side of the engine before the heaters are installed. Use Special Instruction Form No. SEHS7299 to install the 9N3829 Jacket Water Heater Group and make the panel modification. This new group can be installed on 1100 and 3100 Series Engines and 3208 Engines in All Applications.

2. 9N3771 Injection Group (Cetane). This group has a 6 qt (U.S.) tank for the cetane improver additive, solenoid valve, timer, orifice, other parts and two decals. The 9N3771 Injection Group puts the cetane improver additive directly into the fuel system for a reduction of white exhaust smoke. Use Special Instruction Form No. SEHS7253 to install the 9N3771 Injection Group (Cetane) on 3208 Engines in all applications.

3. Ethyl DII2 Diesel Ignition Improver. If an engine uses approximately 25 gallons (94 litres) or less of fuel per day, the engine is probably started many times and operates under low load conditions much of the time. Ethyl DII2 can be mixed with fuel in a bulk tank for daily use. This can keep a higher level of cetane during all conditions of operation. For best results, put the additive in an empty tank or add it while the tank is filled. If the additive is added to a fuel tank, movement of the fuel will mix the additive with the fuel. The chart that follows shows the ratio of Ethyl DII2 Diesel Ignition Improver to the quantity of fuel.

The Ethyl DII2 Diesel Ignition Improver is also the additive used with the 9N3771 Injector Group (Cetane). It is available from:

The additive is available in 5 gal (19.0 litres) and 55 gal (208 litres) drums.

Parts Data

The separate parts of the 9N3771 Injection Group (Cetane) and 9N3829 Jacket Water Heater Group are available for parts service. These parts are as follows: