Dual fuel engine with respective fuel type controllers.

Method/apparatus of controlling a dual fuelled engine which comprises a first controller associated with liquid fuel such a diesel and a second controller associated with a gaseous fuel such as propane or natural gas; the first controller receives engine sensor signals such as accelerator pedal position and is capable of controlling fuel injectors to operate in a liquid fuel mode only; the second controller intercepts the sensor signals, modifies the signals and controls gaseous fuel flow and transmits to the first controller the modified sensor signals to control the fuel injectors in a pilot-ignited gaseous fuel mode, the engine controllers working together to operate the engine in a multi-fuel mode.