PURPOSE: To constrict the dynamic range of an injector by controlling the fuel pressure which is applied to the injection nozzle of the injector in relation to the revolution number of an engine and the suction pressure signal.

CONSTITUTION: A control unit 18 receives a variety of operating parameters from a suction air differential pressure sensor 23, a crank angle sensor 24 and so on. The operation of an electronic control valve 16 which determines the quantity of returned fuel is performed via an electronically controlled valve driving circuit 28 on the basis of the arithmetic operation of the control unit 18 which is performed by the differential pressure detecting signal fed back from a fuel differential pressure sensor 26. By controlling the fuel pressure on the bases of the data of the engine's revolution number and suction pressure, the flow-rate dynamic range of the injector may be constricted apparently.