Abstract: An electromagnetically operable valve for controlling the escape of fuel from the pumping chamber of a high pressure pump includes a valve member slidable in a bore from the end of which extends an outlet about which is formed a conical seating. The valve member is shaped to cooperate with the seating and is urged into contact with the seating when an electromagnetic device is energized. A fuel inlet passage connected to the pumping chamber extends into a chamber defined by a reduced portion of the valve member and the portion thereof which slides in the bore forming a step which defines an annular surface which is exposed to the pressure in said chamber. When the device is deenergized the fuel pressure acting on said surface acts to move the valve member to the open position.