Electrical fuel pump

This type of high-pressure fuel pump as shown in the figure is called a roller cell pump, with the fuel entering the pump and being compressed by rotating cells which force it through the pump at a high pressure.
The pump can produce a pressure of 8 bar (120 psi) with a delivery rate of approximately 4 to 5 litres per minute. Within the pump is a pressure relief valve that lifts off its seat at 8 bar to arrest the pressure if a blockage in the filter or fuel lines or elsewhere causes it to become obstructed.
The other end of the pump (output) is home to a non-return valve which, when the voltage to the pump is removed, closes the return to the tank and maintains pressure within the system. The normal operating pressure within this system is approximately 2 bar (30 psi), at which the current draw on the pump is 3 to 5 amps.
The Fuel passing across the armature of the fuel pump is subjected to sparks and arcing; this sounds quite dangerous, but the absence of oxygen means that there will not be an explosion.
The majority of fuel pumps fitted to the motors of vehicles of today are fitted within the petrol tank of the vehicle and are referred to as (submerged) fuel pumps.
The pump is invariably be located with the fuel sender unit and both units can sometimes be accessed through an inspection hole either in the boot floor or under the rear seat. Mounted vertically, the pump comprises an inner and outer gear assembly that is called the (gerotor).
The combined assembly is secured in the tank using screws and sealed with a rubber gasket, or a bayonet-type locking ring.
On some models, there are two fuel pumps, the submerged pump acting as a (lift) pump to the external roller cell pump.
The second Figure shows typical access to the fuel-submerged pump to measure current draw.
The current drawn by the fuel pump depends upon the fuel pressure but should be no more than 8 amps, as found on the Bosch K-Jetronic mechanical fuel injection which has a system pressure of 75 psi.

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