BENDIX Electric Fuel Pumps: Operation: Notes

Pump operates by the rapid, constant, alternating movement of the pump piston, which rides in the brass tube. When piston spring moves piston up, the upper end of its cylinder enters field force of the magnet. The force of attraction between the magnet and the steel cylinder, causes the magnet, with its angle mounted pole, to tilt against the brass tube, containing the piston. The magnet pivots within the fixture of the circuit breaker, causing ground contact point to press against the mating, fixed contact point, thus closing the electrical circuit. Current begins to flow thru coil windings, creating a strong electromagnetic field in coil and this force overcomes piston spring tension, and pulls pump piston down. As pump piston moves away from the field of force of the magnet, forces of attraction of the magnet anti-pole move the magnet back into its original position, causing the circuit breaker points to reopen. The aforementioned magnetic and electromagnetic action results in fuel delivery in the following manner: When the piston moves up due to piston spring force, it performs the task of fuel delivery as well as fuel intake; on this stroke, fuel transfer valve in piston is closed and inlet valve in valve carrier is open. As a result, fuel held in the area above the transfer valve is raised and delivered to the carburetor thru pump pressure chamber and fuel outlet. At the same time, fuel is drawn into valve carrier from pump inlet and thru open inlet valve. When piston moves down, only an internal transfer of fuel occurs; from the valve carrier, thru the transfer valve, into the chamber within the pump cylinder.