BLACK SMOKE is the most common smoke emitted from diesel engines. It indicates poor and incomplete combustion of the diesel fuel. There are many causes, including:
Incorrect timing
Dirty or worn injectors
Injectors sticking open too long (Common Rail Diesel type)
Over-fuelling
Faulty turbocharger (ie not enough air to match the fuel)
Incorrect valve clearance
Incorrect air/fuel ratio
Low cylinder compression (eg sticking piston rings or worn components)
Dirty air cleaner
Restricted induction system (eg system too small or kinked inlet piping)
Carboned up intake manifolds (esp Common Rail Diesels)
Other engine tune factors
Poor quality fuel
Excessive carbon build up in combustion and exhaust spaces
Cool operating temperatures
BLUE SMOKE is an indication of oil being burnt. The oil can enter the combustion chamber for several reasons:
Worn valve guides or seals
Wear in power assemblies (i.e. cylinders, piston rings, ring grooves)
Cylinder glaze
Piston ring sticking
Faulty turbocharger seals
Incorrect grade of oil (eg oil too thin, and migrating past the rings)
Fuel dilution in the oil (oil thinned out with diesel)
WHITE SMOKE occurs when raw diesel comes through the exhaust completely intact and unburned. Some causes of this include:
Faulty or damaged injectors
Incorrect injection timing (could be a worn timing gear or damaged crankshaft keyway).
Low cylinder compression (eg caused by leaking or broken valves, piston ring sticking, cylinder and/or ring wear, or cylinder glaze)