What does the fuel filter do?

Fuel Filter Image

The filter is designed to capture foreign particles and keep them away from delicate parts of the fuel system. These particles may have been introduced at the while fueling, in the fuel from the gas station, or could be rust from the inside of the car’s fuel tank, especially if it’s an older car.

Not all cars have serviceable fuel filters. Most modern cars have the filter as part of the fuel pump module in the gas tank, which makes replacing them a labor intensive job – if your filter is a separate entity count yourself lucky. On some models the filter is located in the engine bay or on older car, right on the carburetor. Your Haynes manual will be able to tell you where it is in your car, if it has one.

Find Your Car

Every car is different, so find specific instructions in the manual...

When to change your fuel filter

“The engine may stall, it’ll be difficult to start and you’re likely to have a check engine light on the dashboard”

Consult your Haynes manual to see how often the fuel filter should be changed on your car. Some manufacturers advise that no scheduled maintenance is required. If your vehicle has a replaceable filter, replacing it every 3 years or 30,000 miles is a good rule of thumb.

The only time you may need to change your fuel filter is when it’s blocked and is causing engine issues. This fuel starvation will cause the engine to stall, it may be difficult to start and you’re likely to have a check engine light on the dashboard. A blocked filter may damage the fuel pump by making it work extra hard, so it should be replaced as soon as it shows signs of trouble.

You’ll also want to change the fuel filter if you accidentally put gas in a diesel powered car. This will avoid contaminating the system once the tank, pipes and pump have been emptied, flushed and filled with the correct fuel.

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

Warning

The fuel system on a fuel-injected car is under high pressure, so you need to depressurize it before you can remove the filter. Instructions are in your Haynes manual.

How to change your fuel filter

This sample video and instruction is typical for vehicles with serviceable filter. Check your Haynes manual for specific instructions for your vehicle.

  1. Follow the instructions in the Haynes manual to depressurize the fuel system. This involves removing a fuse, unplugging the pump, or some other method of disconnection
  2. Turn the key and try to start the car to remove an residual fuel, then disconnect the negative cable from your battery
  3. Raise the car with a floor jack and support it on jack stands
  4. Locate the fuel filter
  5. Clean the hoses or metal lines on either side of the filter, then loosen the clamps, fittings or banjo bolts
  6. Have rags handy to soak up fuel, and remove the filter
  7. Check that the new filter is identical to the old, and install it oriented in the correct direction
  8. Attach the fuel lines, using new washers or clamps if necessary. Replace any lines that show age or wear
  9. Reconnect the fuel pump or reinstall the fuse
  10. Reconnect the battery and start the car.
  11. Check for fuel leaks once the system has been pressurized

Why you should change your fuel filter

If your car has a fuel filter, it should be changed regularly. A dirty fuel filter will be full of dirt and dust, and in some cases, water. Diesel engines are especially susceptible to water contamination. Anything other than fuel getting into the engine will cause rough running, and possible internal damage.

Dirt and other particles must be kept from entering the fuel lines and fouling the fuel injectors or they may become clogged and need to be replaced. A clogged filter will also put the fuel pump under greater stress, and it could fail, leading to a potentially big repair bill.

Before you begin

Tools you will need

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

  • Floor jack and jack stands
  • Wrench set
  • Ratchet and socket set
  • Pliers
  • Needle-nose pliers
  • Large adjustable pliers
  • Screwdrivers
  • Rags

Parts you may need

  • Filter
  • Gaskets
  • Hose clamps