Electric Fuel Pump - Work, Design and Faults Explained

Autos & TrucksRepairs

  • Author Poline Gruzoff
  • Published March 5, 2011
  • Word count 1,126

Electric fuel pump is used in advanced internal combustion motors to provide fuel coming from the fuel tank to the injectors. The pump have to deliver fuel under high pressure level, allowing the nozzle apply it into the engine. As a way for the appropriate motor performance fuel force per unit area requires to be within just appropriated specs for a sacrificed motor. Excessively low-pressure can lead to "fuel starving" engine misfire, extreme quivering or even quit the motor under load. An excessive amount of force per unit area makes mismatched motor operating excessively rich mixture, or high contamination.

Electric fuel pumps can be installed in fuel reservoir (tank), although some may be used outside. While most machines may be equipped with couple of pumps (one unit inside the tank and the primary unit on the outside). The placement of the pump in the fuel reservoir serves to silence the seething noise of pump's electric motor. Immersion into the fuel aids lubricate and cool the pump's motor. Driving with fuel tank filled with lower than of its fullness could reduce the life of the pump and cause quick overheating. It in addition to this increases risk of fuel pump resulted without of gasolene during rapid acceleration or deceleration.

The pump is always part of a component that along with this consists of a float that transmits electrical motions to the level indicator, sited on the dashboard. In case the fuel pump requires replacing, it can be exchanged individually or the entire component assembly (it is costly, but practically easier).

Different electrical fuel pumps have got unlike types. Some old designs used to employ forced shift of a typical circulation pump chamber. This sort of pump may produce extremely high pressure level and constant flow rate. But at the outlet of a typical fuel pump is actually firm force per unit area variations, from time to time in the gas line soon after the pump was put in damper to minimize the amplitude of impulse of gas pressure. Circling chamber may also be installed outside the tank and combined with the 2nd low pressure pump set up in the fuel tank .

There is another type of fuel pump – "rotor-type". This invention is similar to design of the oil pump and utilizes the offset rotor to bear on the fuel through the pump.

Another version of the roller pump - "vane-type". The blades are used instead of rollers to force the gasoline through the pump.

Most modern autos use a pump turbine. Blades of the impeller pushing gasoline through the pump. Turbine type pumps do not bring forth the pressure level variations these types are less complicated to manufacture and more stable in operation.

It is possible to exchange a fuel pump by not original unit. In this case fuel pump's outflow should be within original specs and fuel intake the same as the original one. Usage of an improper specifications could make impairment of operation of the automobile.

How does the electrical fuel pump operate?

At the time of the ignition, the electronic control unit ECU excites the electrical relay, which provides voltage to fuel pump, its motor begins to revolve, and within a few seconds it makes necessary gasoline pressure. Fuel flows into the intake pump through a meshing filter to delay the corrosion and contaminants. Release of the pump the gasoline passes through the check valve, individual acting (valve keeps a residual pressure level in the system, when pump does not work) and flows to the engine through the fuel line and filter.

The fuel filter captures any rust, contaminants and other solid contaminates that have passed through the pump to keep the incursion of these particles in the injectors.

Farther, the gasolene goes into the fuel rail, placed on the engine and from the rail to each injector. Fuel pressure regulator, placed on the ramp, keeps up the fuel pressure level and flows any extra back to the tank.

Start up the engine and the electric fuel pump begins to function continuously and to maintain pumping gasoline until the engine is operating. If the engine quits, then the electronic control unit ECU gets a signal from the sensing element and the crankshaft ECU will turn off the pump.

A large number of automobiles (specially Fords) have an inertial emergency electric switch which hinders the fuel pump in the case of an accident. It is stipulated to reduce the danger of flame when the fuel line is damaged. To return the emergency sender to its original state - press the reset button on the sensing element.

On older autos fuel pumps controlled at a constant speed. In newer types pump's velocity is being controlled by the electronic control unit ECU in order to exactly correspond permitted specs.

Fuel pump malfunction

The fuel pump can conk out for several reasons :

  • Due to

the presence of contaminates inside the fuel tank (contaminants or

corrosion) ;

  • When driving out of gasoline ;

  • As a

consequence of overheating (in constant movement with a low level of

gasolene in tank) ;

  • Lower voltage (problems with electrical


  • By means of clogging (for a choked fuel filter

excessive resistance of the filter element can make an overload of

electric fuel pump motor.

The harder the conditions of the fuel pump, the more force is required for its performance.

Electric fuel pump frequently goes bad without any warning. You may drive your car without a problem, and within a moment the pump dies, the motor simply stalls and the motorcar gets up in the center of the road. Or in the morning you are going to start the car but the engine simply will not start.

By what symptoms can one anticipate the impairment of the fuel pump? One way is to listen to the noise of the pump when the firing is on. Complete absence of noise points that it is not working. It can be done by a malfunction of the pump, pump electrical relay malfunction, the electrical fuse or the deficiency of voltage.

On most cars when fuel pump dies you would not see usual Check Engine light on. Most modern engines equipped with the module to check the fuel pressure level on the ramp nozzles. Plugging in fuel pressure gauge to the fitting check valve will immediately show whether the pump brings forth pressure level or not. On engines without pressure level test module, to measure pressure level can be done by plugging in directly to the fuel line at the junction of the ramp. If the gauge indicates zero - the pump does not work. If the pressure level is less than nominal, it will be necessary to carry out farther diagnosis to identify the causes of low fuel pressure.

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