Abstract: A shut-off valve for the automotive fuel system is operable to shut off the fuel flow whenever a positive pressure exists in the fuel line between the fuel tank and the shut-off valve. The shut-off valve may be employed in combination with a fuel pump or may be employed separately in the fuel line and comprises a flexible diaphragm connected by a stem directly to the valve member and movable with the valve member. The diaphragm air chamber has an air vent controlled by a vent valve providing a relatively large opening for bleeding in air and providing a relatively small opening for exhausting air from the diaphragm air chamber. The vent valve thus permits a relatively fast movement of the valve member to an open position and a relatively slow or restricted movement of the valve member toward a closed or partially closed position.