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Project EFI

After unloading the Rover SD1 EFi, the engine did not start. A basic test and check procedure made it clear that the fuel pump did not suppy fuel. The pump is located somewhere below the car, near the driver seat, and not as in the carburetor inside the fuel tank. It is powered with 12 volt DC, which is switched by a mechanical switch inside the airflow sensor. See picture.

Electric Fuel Pump

The electric fuel pump is a roller-cell pump driven by a permanent magnet electric motor. The rotor plate which is eccentrically mounted in the pump housing is fitted with metal rollers in notches around its circumference which are pressed against the pump housing by centrifugal force and act as seals. The fuel is carried in the cavities which from between the rollers. The pumping action takes place when the rollers, after having closed the inlet port, force the trapped fuel around in front of them until it can escape from the pump through the outlet port. The fuel flows directly around the electric motor. There is no danger of explosion, however, because there is never an ignitable mixture in the pump housing.

The electric fuel pump delivers more fuel than the maximum requirements of the engine so that the pressure in the fuel system can be maintained under all operating conditions. A check valve in the pump disconnects the fuel system from the fuel tank by preventing return flow of fuel to the tank.

The electric fuel pump starts immediately when the ignition and starting switch is operated and remains switched on continuously after the engine has started. A safety circuit prevents fuel from being delivered when the ignition is switched on, but when the engine is stationary (e.g. after an accident). The fuel pump is located in the direct vicinity of the fuel tank, below the driver seat (LHD) and requires no maintenance. The armature and bearings are cooled and lubricated by the fuel flowing through the pump with no risk of combustion because the pump never contains an ignitable mixture, even when the tank empties.

The pictures shows the eccentric rotor mounted on the armature shaft with rollers in pockets rotating within a housing. When the motor is energised centrifugal force acting on the rollers forces them outward to act as seals. The fuel between the rollers is forced to the high-pressure side of the system.

A pressure relief valve is located within the roller pump prior to the armature and protects the pump from over -pressurising. A non-return valve is located in the pump outlet to the filter and injectors; it prevents fuel draining from the injector supply pipe.

Fuel gravitates through a filter in the tank to the pump inlet and into the roller pump ensuring that the system is primed. The roller pump generates the necessary fuel pressure to feed the injection system. Excess pressure opens the relief valve allowing fuel to recirculate to the pump input.