Abstract: A control system is provided for regulating the fuel feed to a dual fuel internal combustion engine. The engine includes a source of first fuel, a pump therefor, and a source of second fuel under a predetermined pressure. A first valve is mounted within a first feed line connecting the engine to the pump outlet. A second valve is mounted within a second feed line connecting the engine to the pump outlet. A third valve is mounted within a third feed line connecting the engine to the second fuel source. A pressure-sensitive metering valve is disposed within the third feed line downstream of the third valve. A means is provided which transmits the flow pressure from the second valve to the metering valve and thus, determines the setting of the latter. A control means, adjustable between two modes, is operatively connected to the first, second, and third valves.