These are used by many automotive manufacturers including Daimler Chrysler, Ford, General Motors, Honda, Hyundai, Jaguar & Volkswagen as a safety device. Its purpose is to shut off the fuel pump(s) in case of an accident, preventing fuel from being continually pumped and spilled over the vehicle if there is a leak in the system.
The fuel cut off switch, is designed to instantly stop fuel flow is very similar to a relay. It has a pair of contacts that are linked to the vehicle electrical system and allows current flow through them to run the fuel pump(s). When the switch is closed, the circuit is complete, and the pumps will operate.
The switch is different in that Instead of a solenoid coil or thermal expansion device that a conventional relay uses to break the circuit, this switch uses a mechanical device consisting of a steel ball in a funnel. The ball is held in place by a magnet at the bottom of the funnel. When subjected to shock, the ball breaks away from the magnet and rolls up the side of the funnel, hitting the actuating arm of the switch mechanism.
When the ball pushes against the bottom of the actuating arm, it moves it up, and the linkage in the switch “opens” the electrical circuit and cuts off power to the pump(s). Once actuated the circuit then remains in the “open circuit” position until it is reset.
