Diesel engine white smoke at startup

What could make a diesel engine produce white smoke? Can bad diesel cause white smoke? Why does diesel engine produce black smoke on start-up? What makes a diesel blow blue or white smoke?

The white smoke is due to unburnt fuel caused by improper heating. When it’s cold outside and you notice white smoke at startup , then you probably have nothing to worry about. Diesel engines need high compression and heat for fuel combustion.

When the warm or hot exhaust gases meet cold outside air, condensation and steam is a result. After a short amount of driving , the white smoke should lessen. In very cold temperatures, the heated exhaust can freeze into minute fuel droplets when exiting the exhaust and produce a more prolonged emission of white smoke for a very short period of driving time.

This typically occurs due to the engine being too cool to burn the fuel , often resulting from low compression in one cylinder, problems with the fuel injection timing or a defective fuel injector. This will cause white smoke , along with the idle issue. Use of our Flushing Oil Concentrate and FTC Decarbonizer address these respective problems. Water entering combustion spaces will also create white smoke. Normally, it would happen at startup in cold weather with lower compression engines and retarded timing.

Has the engine got a fuel pre-heat system for starting in cold weather? If the pre-heat ceases to function it can be like electing a pope for several minutes until the engine warms up. This is because the two stroke engine have back up oil which normally enters the fuel chamber to lubricate the piston. This is a case where you’ll probably want to call in the diesel pros, but here’s a diagnostic tip: While the engine is smoking, hold your hand over the exhaust outlet for seconds or so. When the engine is cold or has cooled back down I get a lot of white smoke at startup.

Usually, white smoke indicates that the diesel fuel is not burning correctly. Unburned diesel fuel will make its way through the exhaust completely unused. Be careful of white smoke as it will irritate your eyes and skin. If white smoke occurs during a startup in freezing temperatures, then goes away, it usually indicates frozen deposits of soot which expanded around the rings then burned away once the engine warmed up. Heavy duty diesels and most trucks emit some white or black smoke on startup or accelerating.

It is often a result of bad driving technique (lugging), poor injector maintenance, or excessive fuel delivery rates. It may also be a combination of all three. Gray, black, or white smoke emissions are warning signs.

This is due to the fact that colder air, which is more dense than warm air, lowers temperatures in engine cylinders at the end of the compression stroke. This colder air leads to reduced combustion of the fuel that has been injected into cylinders. That won't be white smoke , it will be un burnt diesel. When you start the engine , the wispy white ‘ smoke ’ isn't smoke at all, but the vapor going into the air due to the heat. Since this is a boat and marine diesel forum, an white smoke seems to come with the territory, I’ll first start by giving you about twenty years of personal experience with white smoke.

White smoke on start up.