White smoke occurs as a result of combustion temperature being so low that only partial combustion occurs, and the partially burned fuel that exits the exhaust is in the form of a white smoke vapour. Technically, the white color is caused by the light-scattering characteristics of the re-condensed droplets of fuel (unburned or partially burned) larger than one micron.
Many factors contribute to this condition, including the following:
1. Poor fuel quality (low cetane rating).
2. Low inlet air temperature.
3. Low coolant temperature.
4. Low compression ratio.
5. Retarded (incorrect) ignition timing.
6. Incorrect/failed fuel injection components.