A control valve for controlling the movement of a needle of a fuel injector includes a coil which is attached to a housing of the injector, which housing engages with an armature which can be moved between an open position and a closed position. The armature includes a magnetic plate, through the center of which a rod, which forms a valve piston, extends perpendicularly to the plate to a remote end. The piston slides into a bore in the injector housing, the movements of the armature and of the piston opening or closing channels in which pressurized fuel flows. The armature is provided with a device for quickly discharging the fuel which is captive between the coil and the plate.