Dual fuel control and supply system for internal combustion engines

An electronically controllable dual fuel system for an internal combustion engine having a liquid fuel injection system incorporating an injector pump for delivering prescribed quantities of a principal liquid fuel under pressure to individual injectors for the cylinders of the engine, comprising:

• an electronic control unit,
• an electrically controllable first variable flow regulator arranged to receive a combustible alternative fuel under pressure and deliver controlled quantities of said alternative fuel to the engine as determined by electrical signals received by and transmitted form said electronic controlled unit,
• a by-pass control system, including:
• by-pass bleed means for bleeding liquid fuel from the principal liquid fuel injection system at the output side of the injector pump and before the injectors and by-passing the bleed fuel through the by-pass control system,
• a second electrically controllable variable control regulator to control the quantity of principal liquid fuel capable of being bled and by-passed from the output side of the injector pump, and
• a by-pass flow meter arranged to measure the quantity of principal liquid fuel bled from the output side of the injection system and supply a corresponding electrical signal to said electronic control unit,
• said electronic control unit determining the energy value of the proportion of principal liquid fuel normally intended to be supplied to the engine to meet the engine's demands at that time but bled from the injection system and controlling the prescribed amount of electric power to said variable flow regulator to enable delivery to the engine of the prescribed quantities of alternative fuel proportional in energy value to that necessary to maintin the required power rating and/or speed of the engine for normal efficient operation.