Fuel Pump: Description and Operation

Fuel Pump:

Two electric fuel pumps (in series) which are located under the rear of the vehicle, supply a high rate of fuel to the injection system. Operation of the pumps are controlled by the fuel pump relay. The relay energizes the fuel pumps briefly (approx. 1.5 sec.) when the ignition is turned "ON", during cranking (starting), and while the engine is running. The CIS-E control unit supplies the engine speed signal as an input for fuel pump control.
In order to maintain the pressure in the fuel system under all possible operating conditions, the pumps supply substantially more fuel than the engine needs at maximum engine loads.

Fuel Pump:

The roller-cell pumps consist of a cylindrical hollow chamber in which an eccentrically fitted rotor disc rotates. This is fitted with metal rollers which are held in pocket-shaped recesses around the circumference. When the rotor disc rotates the rollers are pressed outwards by centrifugal force and act as a circulating seal. A pumping operation is effected by the circulating roller seals which draw in fuel at the inlet port and forces fuel through the outlet port against the pressure regulator. A non-return valve in the pump prevents fuel from flowing back to the tank, as well as decoupling the fuel system from the tank.