Ah, the whiff of diesel smoke. But which one?
Blue-white smoke:
Blue-white smoke may be noticed at engine start-up whether the engine is at normal operating temperature or not. Blue-white smoke can be observed at all ambient temperatures and should not last longer than a minute or two after start up. Blue-white smoke can return when ambient temperature is below 10C, the engine is warmed up but this is followed by extended idling. This is due to combustion chambers cooling down.
If you see continuous Blue-white smoke while driving, then air may be being sucked into the fuel system.
White smoke:
White smoke and blue-white smoke share some of the same characteristics. White smoke is fuel not being burned. Extreme white smoke can be caused by the combustion chambers cooling down or the fuel not igniting at all. One cause of this could be incorrect injection pump timing. Coolant getting into the combustion chamber can cause white smoke also. Possible causes are blown head gaskets, cracked heads, etc.
Black smoke:
Black smoke is caused by an over rich mixture and can also occur when a properly adjusted engine is working hard and being overfueled e.g. during heavy acceleration. Clogged air filters are also a favourite cause of black smoke.
Blue smoke:
Blue smoke is not normal. Blue smoke occurs when oil is entering the combustion chamber and is burning along with the fuel. Blue smoke usual indicates a condition which should be corrected a.s.a.p. Blue smoke also smells like oil burning. Possible causes include valve seals or cracked piston rings.
