Abstract: A heating device for mounting on an air inlet manifold of a compression ignition engine to heat the air flowing to the engine comprises a thin walled tubular element closed at one end and having a fuel inlet at the other end. A ceramic plug is located in the element to direct fuel flow against the interior surface of the element. A heating element is wound about the tubular element to heat and vaporize the fuel which flows out through an opening adjacent the one end. The fuel vapor forms an air/fuel mixture which is ignited by an ignition element.