Abstract: A circuit for controlling the operability of an electrically-operated fuel system, for a vehicle, and particularly for controlling a fuel injection system. The circuitry includes a timing network and a concealed switch the position of which is only known to an authorized operator of the vehicle. When the concealed switch is closed by an authorized person an associated relay is energized and the timing network is inhibited which in turn maintains a main control relay in its enabling position permitting normal operation of the fuel system. In this authorized mode of operation the timing network is essentially maintained in a state where it is not permitted to time-out. When an unauthorized person gains entry to the vehicle, by-passing the ignition switch, the concealed switch is not closed, nor is the associated relay energized.

Abstract: A solenoid-operated valve is disposed in the fuel line of an automobile to interrupt the fuel flow to the carburetor when the solenoid is deenergized. The solenoid operated valve is maintained in its fuel-open position only when both the automobile ignition switch is closed and a supplementary concealed switch is closed. The circuitry for operating the valve may include either a relay or an electronic device. An indicator light is illuminated during the fuel-closed position of the solenoid operated valve as a reminder that both switches must be operated to permit vehicle movement.