Bad Fuel Filter Symptoms

Updated on April 13, 2016
A clogged fuel filter can leave you stranded on the road.
A clogged fuel filter can leave you stranded on the road. | Source

Is your car feeling sluggish on the highway? Is it hard to start sometimes? You should be worried. It can get much worse pretty soon if you're dealing with a clogging fuel filter.

Yes, fuel filters don't last forever.

Over time the filter element clogs, restricting and blocking fuel flow. That's why most manufacturers suggest fuel filter service intervals as part of your car's preventive maintenance.

Check these signs of bad fuel filter symptoms to avoid getting stranded on the middle of the road and paying an expensive repair bill.

A check valve in a clogged fuel filter will pass unfiltered fuel and damage fuel injectors.
A check valve in a clogged fuel filter will pass unfiltered fuel and damage fuel injectors. | Source

Signs of a Clogging Fuel Filter

The fuel filter removes abrasive particles, sediment, rust, dirt and other contaminants from the fuel stream that can upset the operation of a carburetor, fuel injector or diesel injection pump, and ultimately affect engine performance.

* As driving miles accumulate, these particles spread over and stick to the filter element.

* As particles start to clog the filter, the rate of fuel supply begins to decrease. You may not notice it while driving in stop-and-go traffic, but as soon as you accelerate to highway speeds, the engine hesitates or misfires—the rate of fuel fed to the engine can't meet the most demanding needs of your engine.

* Soon, you won't go too far from your driveway before your engine dies.

* At this point, your fuel pump might have suffered some damage since the clogged filter is putting too much pressure on the pump.

And you might be lucky if your clogging filter gives you these signs. A few years ago, some manufacturers decided to install a check valve in some of their filters. This valve begins to open whenever working pressure inside the filter starts to rise, so that fuel bypasses the clogging filter element. This way the engine doesn't loose power or stalls, which in a way is a good thing. However, this can have catastrophic results for your engine over time if you are not paying attention to your car maintenance schedule.

Allowing unfiltered fuel to pass can wreak havoc with your engine, as hard particles can scratch cylinder walls before impurities begin to shut off your carburetor or fuel injectors. Later on, you'll have to deal with a more expensive repair.

Watch the next video so that you have an idea how a filter degrades after just one year of operation.

The Fuel Pump Restrainer

You can see similar symptoms to those of a restricted or clogged in-line fuel filter when the in-tank fuel pump restrainer (or mesh filter) begins to clog as well.

The restrainer catches big particles inside the tank to protect the fuel pump. However, you may have a harder time troubleshooting for a clogging restrainer than a bad fuel filter. Soon after your engine stalls, the restrainer may partially clear and allow your engine to start, until it clogs and your engine stalls again. If you replace the fuel filter and the problem continues, you might not realize the restrainer is the one clogging.

Common Symptoms of a Bad Fuel Filter
Car feels sluggish at highway speeds
Hard starting

Replacing the Fuel Filter

If you haven't changed the fuel filter in more than a year, chances are your problem lies in a partially restricted or clogged fuel filter. And, even if this is not your main problem, you got nothing to lose by replacing a filter with an overdue service date.

Most in-line fuel filters are pretty straight forward to replace. Unfortunately, many modern vehicles have moved the filter inside the fuel tank. So you need to lower the tank, and pull out the fuel pump to replace the filter. Still, other models require replacing the whole fuel pump assembly as part of the fuel filter replacement service. If you have some mechanical experience, you might be able to replace this in-tank filter. Check the repair manual for your particular vehicle, if necessary. It'll show you the proper procedure for your particular model.

On some vehicle models (both gasoline and diesel) you may find a bowl fuel filter. This is a device in the engine compartment. Maintenance requires opening the canister, cleaning the bowl and replacing the filter element. And some diesel engines may use a canister fuel filter, similar to the bowl type filter and requires the same type of maintenance.

If you've decided to change the fuel filter, work in a well ventilated area and park your car away from appliances that work with natural gas. Fuel fumes are highly flammable and might reach the pilot light in a water heater or clothes dryer and cause a fire.

Basically, when replacing an in-line fuel filter:

* You'll need to relieve system pressure first. On some models with TBI (throttle body injection) systems, you can remove the fuel pump fuse, start the engine and let it idle until it stalls. Then crank the engine for about three seconds and you are ready to replace the filter.

* Multiport fuel injection engines use a Schrader (service) valve on the fuel rail, near the engine (the valve looks like a tire air valve). Although the correct way to relieve pressure through this valve is with a fuel pressure gauge and a bleeder hose attached to it, I've done it by removing the fuel filler cap, and then using a shop rag to catch the small amount of fuel that squirts out through the valve as I depress it with a screwdriver. This works nice if you are working on a cool engine; on a hot engine, you may cause a fire if you accidentally spray some fuel around.

* Once you've relieved system pressure, you can remove the filter. Some models use a plastic, hairpin clip on each side of the filter to lock the fuel lines in place. On other models you need to unscrew a threaded fitting using a line wrench to prevent damage to the lines. Still, other models may use a special snap-on connector to attach the line to the filter. This requires a special tool to separate the line from the filter. On some vehicle models all you have to do is unscrew the filter bowl cap, pull out the filter element, install a new one, and replace the cap. Check your repair manual, if necessary.

* Take the old filter with you to the parts store and match it to the new one so that you know you got the right replacement.

An in-line fuel filter may be located near the fuel tank.
An in-line fuel filter may be located near the fuel tank. | Source

If your car is showing one or more of the symptoms described in the previous section, you may have a partially or clogged fuel filter. Check your car owner's manual to locate the filter and check the recommended maintenance schedule. And, if your car is not experiencing any of these symptoms yet but your filter has reached the manufacturer service interval, replace the fuel filter now. Always try to follow the filter service interval recommendations in your car owner's manual or a schedule that fits your driving habits and conditions. Unfortunately, some manufacturers don't include a service interval for the fuel filter. If you don't find the service interval in your maintenance schedule, replace it at least once a year to prevent engine performance issues.

How often do you replace the fuel filter?

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Questions & Answers


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      • Dan Ferrell profile image

        Dan Ferrell 9 months ago

        Hi IN,

        You can safely follow the manufacturer standard of 15,000Km and 7500Km for the oil and oil filter respectively.

        Air filter are usually changed every year, if you drive at dusty environments, so you want to inspect it at least every 12 months. If it looks like it's clogging, replace it. Otherwise check it every 6 months afterwards and replace it as necessary.

        Good luck

      • profile image

        Ishmael Nyarko 9 months ago

        How often should I change my 2007 pajero diesel filter and air filter?