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How to change a fuel filter

How to change a fuel filter

Your car’s fuel filter performs the crucial job of stopping any pollutants from getting inside the engine, keeping your car running smoothly and ensuring optimum fuel efficiency. However, it can only do this if it’s kept in good condition.

Changing the fuel filter is one of those basic maintenance jobs that all vehicles need from time to time. In this guide, we’ll explain how the fuel filter works, how often it needs replacing, and how to change it. We’ll cover:

Please note that the advice in this guide refers to petrol filters only. The fuel systems in diesel cars are more complex, and the fuel lines are highly pressurised, so it’s better to ask a professional for help.

How does a fuel filter work?

How does a fuel filter work?

Modern car engines are made up of a lot of delicate, high-spec parts and so have a tight tolerance for contamination. That means they can be very adversely affected by even the smallest amount of dust, rust, or dirt. If any of these pollutants get inside the fuel tank — say, during the re-filling process — then the fuel injectors and other delicate parts will quickly become damaged, meaning costly repairs for you.

The fuel filter works by filtering out any harmful contaminants before they can reach the engine. This means that it’s inevitable that pollutants build up in the filter over time, and the part is designed accordingly. However, if left for too long, the filter can become blocked or clogged and interfere with the flow of fuel into the engine.

Should the blockage become very severe, the engine could struggle to generate enough power to get your car going, meaning the car won’t start at all. So, it’s important that the fuel filter is checked regularly and, when necessary, changed or cleaned. The correct way to maintain your fuel filter will vary from vehicle to vehicle, so check your owner's manual to learn more about this.

Types of fuel filter

There are a number of different types of fuel filter, but the most common varieties are cartridge filters and modern strainer-type filters.

Cartridge fuel filters are designed to be serviceable parts, meaning they don’t last forever and need to be replaced every few years. The cartridge filter contains a special type of porous filter paper or other fine material that is effective at catching tiny particles of dirt or dust while still allowing fuel to pass through.

This type of fuel filter is usually located between the fuel tank and the injectors. In some models, the filter is accessible via the bonnet, while in others, it can only be accessed underneath the vehicle. Your car owner's manual or Haynes manual can help you locate the filter on your vehicle.

Many newer cars don’t use a replaceable filter cartridge and have a strainer fitted inside the tank or on the pump, instead. This isn’t a serviceable part so, if there’s a problem with it, it’s best to consult a professional.

How to know if your fuel filter is bad

It can be tricky to diagnose a bad fuel filter, as they usually tend to be sealed units, meaning it's not easy to tell that they're blocked or clogged just by looking at the part. The best solution is usually to change the filter if you notice any of the symptoms we've shared below.

The symptoms of a bad fuel filter

The symptoms of a bad fuel filter

It’s normal for a replaceable fuel filter to become dirty over time: it means the filter is doing its job as it should. However, if the filter becomes so dirty that the flow of fuel to the engine is disrupted, then it can cause serious issues. So, it’s important that you can recognise the signs of a blocked or clogged fuel filter.

If you have a bad fuel filter on your hands, you might notice the following symptoms:

The car struggles at lower speeds or on hills

If your car is fine while cruising down the motorway in fifth gear but starts struggling while driving slowly, a dirty filter could be to blame. This is because a blockage in the fuel filter is disrupting the flow of fuel to the engine, which means the car can't generate enough power to tackle hills or to accelerate in lower gears.

The same goes for driving on hills: the engine must work harder to power the car up the slope, which requires more fuel. So, if you notice a lack of power when accelerating or driving up hills, a clogged fuel filter could be to blame.

The engine stalls while running

If a blockage inside the filter is partially disrupting the fuel supply to the engine, then it might cause the engine cut out while driving. This is because the blockage in the filter will prevent fuel from reaching the engine, causing the engine to stall. You can still start the car initially, as there’s enough fuel inside the lines to get the engine going. However, once this is used up, the engine will fail.

How often should a fuel filter be changed?

If your car has a replaceable fuel filter, then it should usually be changed once every three years or 30,000 miles (whichever happens first). However, this can vary between different makes and models, so you should always check the owner’s manual or Haynes guidebook for your car.

It may also need changing earlier if you’ve noticed the symptoms of a bad fuel filter. If you suspect a blockage, don’t put off replacing the filter: a clogged filter will force the fuel pump to work overtime, making it more likely to wear down or break. And that would lead to much more extensive — and costly — repairs. So, always change the fuel filter at the first sign of trouble.

The engine warning light is on

Most cars aren’t equipped with a sensor that can tell you if the fuel filter is dirty or clogged, but there is a possibility that a dodgy fuel filter could trigger the engine light on the dashboard. So, if you’re getting a 'check engine' warning on the dash and you’ve noticed other symptoms on this list, it could be caused by a bad filter.

The car won’t start

If the engine won’t start at all, then it could be because a blockage or build-up in the fuel filter is cutting off the fuel supply to the injectors, meaning there’s not enough fuel to ignite the engine.

Of course, there may be lots of other reasons that the engine won’t start — take a look at our car starting problems guide to find more information that will help you diagnose this problem. But, if the engine won’t kick into gear and you’ve already noticed some other symptoms in this list before it died, a bad fuel filter could be the culprit.

How to change a fuel filter step by step

How to change a fuel filter step by step

Changing a fuel filter is a job that most amateur mechanics with a bit of automotive knowledge should be able to complete. However, you should be aware that, while it’s not an especially complicated job, it can be a messy one. So, we’d advise wearing old clothing when carrying out these repairs.

Please note that the following advice is intended for petrol vehicles with serviceable fuel filters only. The fuel filters in diesel cars are much more complicated, and the pressure levels inside the lines can be very high, meaning it can cause injury if not handled correctly. Check your owner’s manual or Haynes guide for more information about this.

You will need the following equipment:

  • A replacement fuel filter: This needs to be the correct type for your car. You can check the make and model in the owner’s book or use the product finder on our fuel filter page to ensure you buy the correct parts.
  • Replacement fuel filter clips: These small but essential fittings are usually made from plastic and may break when being removed, so it’s a good idea to have some replacements on hand.
  • A bowl, bucket, or container: This is to catch any fuel run-off during repairs. Be sure to choose one that can safely contain petrol.
  • Rags and newspaper: For cleaning up spills and catching drips.
  • Assorted hand tools: Including tweezers, pliers, wrenches, a socket set, and screwdrivers.
  • A trolley jack.
  • Eye protection and gloves.

Once you’ve got everything ready, you can suit up and get to work.

  • 1. De-pressurise the fuel system. First, you need to disable the fuel pump in order to relieve the pressure inside the fuel lines. The simplest and safest way to do this is to remove the fuel pump fuse from your car’s fuse box. This will prevent the pump from running when the engine is on, allowing the pressure in the fuel lines to drop to a safe level. To do this:
    • I. Locate the car fuse box using your owner’s manual. Most cars have two: one under the bonnet and one in the cabin. The manual will show you which one contains the fuel pump fuse.
    • II. Identify and remove the fuel pump fuse. There should be a fuse diagram on the fuse box to help you with this. Using a pair of tweezers will help you to remove the fuse if you’re finding it tricky.
    • III. Check the car is in neutral or park and that the handbrake is on. The pump won’t be working and so no more fuel will circulate through the system, but there will still be a bit of fuel left in the lines that could cause the car to start moving. And, you certainly don’t want that. So, make sure the car is in neutral or park and that the brakes are firmly on.
    • IV. Start the engine. Hit the ignition and let the car run for at least a couple of minutes. Then, switch it back off. This should be enough to depressurise the fuel lines.
    • V. Replace the fuel pump fuse. Place the fuse back where you found it. Don’t restart the engine again after this, as you don’t want to repressurise the fuel lines.

Once you’ve safely depressurised the fuel system, you can move onto replacing the fuel pump.

  • 2. Disconnect the car battery. You can do this by removing the negative battery cable using a socket wrench. This will stop the car from accidentally starting up while you work.
  • 3. Locate the filter. You may need to jack up the car to do this, depending on whether the filter is on the underside of the car or under the bonnet. If so, raise the car now.
  • 4. Prep the repair area. Clean the fuel lines and surrounding areas with a rag or cloth to make it easier to work.
  • 5. Loosen the clips, fittings, or bolts holding the filter in place. This will make it easier to remove the filter.
  • 6. Place your bucket or container underneath the filter to catch any run-off. Even though the pressure in the system has been reduced, there will still be some fuel in the system that will spill out when you disconnect the filter from the fuel lines.

Tip: Remember to dispose of any excess fuel safely by taking it to a recycling centre that accepts chemical waste.

  • 7. Remove the clips. Most filters are fitted with two clips: one at each end of the filter. Use your fingers or a flat-head screwdriver to gently prise them free. These clips are often made from plastic and break easily, which is why we recommend having some spares on hand.
  • 8. Look at the old filter before you disconnect it. It should have arrows to show you which way round it should be installed. This will show you which way round the new filter should face. Put on your gloves and eyewear (if you haven’t already).
  • 9. Disconnect the fuel lines. To do this, you’ll need to slide the lines away from the filter until they pop off. At this point, some fuel is likely to splash out, so be ready for this and try to angle the end of the fuel hose towards the bucket or container to help catch it.
  • 10. Remove the filter. It will usually be held in place by a the fuel filter housing. Now that both fuel lines are disconnected, you should be able to pull out the filter by sliding it towards the front of the car. Some filter brackets are secured with a bolt, so check for this before you try to take the filter out.
  • 11. Compare the old and new filter. Once the filter is removed, lay it side by side with the replacement and compare the two parts. They should be exactly the same size and shape. If the replacement doesn’t look right, return it and find a new one. Never attempt to fit a part that doesn’t look right, as this could cause serious damage to the entire fuel system and engine when you next start the car.

Tip: Comparing old and new parts is a simple but effective way to make sure you’ve got exactly the right part for the job during almost any kind of replacement work. It never hurts to double check!

  • 12. Fit the new filter. You can do this by sliding the filter into the bracket or clip. It should be easy to do, and the filter should fit snugly into the bracket. Replace any bolts, if needed.
  • 13. Reconnect the fuel lines. The lines should slide back onto the nozzles at either end of the filter.
  • 14. Replace the clips. Be careful not to force them, as they tend to be quite delicate. Once the clips are in place, the new filter should be securely attached to both fuel lines.
  • 15. Finish up. Clean up any mess, run off fuel, and lower the vehicle (if raised). Once the vehicle is safely lowered, you can reconnect the negative battery cable. Well done — the job is now finished!

Knowing how to change a fuel filter is an essential part of basic car maintenance, and it can save you money on professional repairs at the garage, too. Here at GSF Car Parts, we have all the fuel system parts you'll need to keep this important part of your vehicle running smoothly, including hoses, fittings, pressure control valves, and more. And, with our helpful product selection tool, finding exactly the right part for your car couldn't be easier — just enter your car's registration and we'll do the rest. We also have fuel additives that are great for giving your car a quick and easy boost.

If you have questions about any of our parts, don't hesitate to contact us on 0121 626 7971. You can also find lots more helpful advice in our automotive knowledge hub, including essential maintenance tips on how to change an oil filter, how to check and change car batteries, and other repair work.