Abstract: Disclosed is a valve for selectively preventing fluid flow along a flow line. A plunger of a locking mechanism moves a valve stem between a first position, in which the valve is in an open configuration, and a second position in which the valve stem presses a resilient diaphragm into sealing engagement with an annular seat circumscribing an outlet port resulting in a closed configuration for the valve. The valve stem may be moved from the second position to the first position only by unlocking the locking mechanism. In the embodiment shown, the valve is interposed along a fuel flow line between a fuel supply and an engine in a motor vehicle. Inlet and outlet flow line receiving means are integrated in a plastic housing, which includes two components riveted together.