Abstract: The invention relates to a control device for a multiple cylinder-piston motor for operation with a gaseous fuel, said control device being connected to the gas conduit, leading from the throat of the venturi-tube in the air suction conduit to the evaporator pressure regulator, as well as to the vacuum conduit, leading from downstream the throttle in said air suction conduit to said evaporator-pressure regulator, said control device comprising a control valve provided with a control mechanism, said control valve being incorporated in said gas conduit and said control mechanism being incorporated in said vacuum conduit, the arrangement, on operation of said throttle from its closed position towards its open position, and reverse, allowing the said control valve to be automatically brought from a position for small gas passage to a position for considerable gas pressure, and reverse.