Thread: smoke on start up

Originally Posted by Blknight.aus

black smoke is normal...

its to do with the governor.

very very basically

when the engine is stationary there is no resistance to the full fuel spring so the engine gets full fuel for start up, theres no dynamic advance wound in so injection is happening later than normal for the first couple of firings.. as the engine speeds up the governor flyweights take over and bring everything back to idle (or whatever engine RPM is being requested by the throttle input)

You have just shattered an illusion that have held for some time.

I knew that 300TdIs blew a puff of black smoke on startup. I had assumed that it was some fiendishly clever aspect of the design deliberately incorporated to reduce the need to use the glow plugs for cold starts.

Are you telling me that rather than something deliberately engineered into the fuelling system of the 300Tdi, that it is just an unintended, though useful, consequence of using an antiquated mechanical governor?

With diesels:

Black smoke indicates incomplete combustion leading to soot particles in the exhaust. Engine not properly warmed up, or if warmed up, then too much fuel for the available air. If it is lack of air, then it could be a turbo, or boost leak problem.

White smoke when a cold engine is starting is not a concern. It indicates fuel that has not burned.

Blueish, grey smoke indicates engine oil is being burnt, i.e. oil bypassing rings, valve stems, or turbo seals.

I rather think from the original post it is not much to be concerned about.