How an engine’s fuel pump works

Fuel Pump Image

Your car’s fuel pump, like all cars with fuel-injected engines, is an integral part of the fuel tank. It comprises an electric motor and sends fuel under high pressure to the engine’s fuel injectors via fuel lines.

On some cars the fuel pump, fuel level sending unit and fuel filter may need to be replaced together. Haynes will advise you if that’s the case and will provide full instructions on how to change it.

The fuel pump’s operation is controlled by the car’s ECU. In the event of an accident the fuel pump can be shut off to reduce the likelihood of an engine fire starting.

This task requires experience and a good tool kit. This job will take four to five hours to complete.

 

Every car is different, so before you view the full instructions, find yours…

When to change your fuel pump

“The symptoms of a faulty fuel pump may be confused with a clogged fuel filter or mis-fuelling”

There are several signs that a fuel pump is on the way out. The most obvious is that the car won’t start, because the pump is unable to get the fuel to the engine. It’s likely that other symptoms will have shown themselves first, though.

These include a loss of power when accelerating, an intermittent stuttering when running at higher speeds and an unexpected surge in acceleration because the pump cannot maintain a constant fuel pressure.

The symptoms of a faulty fuel pump may be confused with a clogged fuel filter or mis-fuelling, so it’s important to get the problem diagnosed properly before you begin work - an error code generated by the onboard computer is a good place to start.

All cars are slightly different, so if it is time to change your thermostat, use our before you begin checklist, and find your car for specific instructions.

 

How to change your fuel pump

This is a clip from a sample video. Find the full step-by-step task for your model.

A very brief summary of the task:

  1. Relieve the pressure in the fuel system
  2. Access the top of the fuel tank and undo the electrical connectors and pump lines
  3. Loosen the module retaining ring, remove the assembly and remove the module from the tank
  4. Install a new seal on the fuel tank, fit the new module and tighten the retaining ring

Tools you will need

A comprehensive toolkit may be needed for this task, depending on your model

  • Floor jack (if necessary). Not your car’s emergency jack
  • Axle stands
  • Fuel pressure gauge with bleed-off valve/drain hose
  • Spanner set
  • Socket set
  • Pliers
  • Needle-nose pliers
  • Large adjustable pliers
  • Flat-bladed screwdriver
  • Phillips screwdriver
  • Rags
  • Power drill

Parts you may need

 

Fuel pump £80-£300*

*Price varies hugely depending on model

Seals £10
Garage fee savings £300-£500
 

Every car is different, so before you view the full instructions, find yours…