Bad Fuel Filter Symptoms, Causes, and Other Important FAQ

Written by

CarParts.com Research Team

Automotive and Tech Writers

Updated on January 9th, 2025

Reading Time: 4 minutes
Summary
  • Difficulty starting your car, sluggish acceleration, and rough idling are common symptoms of a dirty fuel filter.
  • A fuel filter is specifically designed to prevent natural impurities, debris, and other contaminants found in gas from entering the fuel system.
  • As the fuel filter does its job, it’ll naturally collect many contaminants over time. This is why most manufacturers recommend replacing the fuel filter every 20,000 to 150,000 miles.

In order to function properly, the engine needs a sufficient supply of clean fuel. A fuel filter helps achieve this by trapping dirt and other contaminants before they can enter the engine. Over time, however, it’ll collect too much dirt and interfere with the flow of fuel. You’ll need to replace it before it starts causing problems for your vehicle.

What Are the Symptoms of a Dirty Fuel Filter?

To help you determine if your fuel filter needs replacing, here are common signs to look out for:

Difficulty Starting Your Car

This is one of the most common signs of a blocked fuel filter. Turning on the ignition causes the fuel pump to send gas from the tank to the engine. However, a dirty fuel filter will block the fuel, preventing it from reaching the engine and preventing it from starting.

Sluggish Acceleration

Even if you successfully start your car, there’s still a chance for the engine to perform poorly. Your car struggles to accelerate because the dirty fuel filter inhibits gas flow, preventing the engine from getting enough fuel.

Rough Idling

Without enough fuel, your engine is also likely to idle rough. The low fuel pressure can also cause your engine to lurch or misfire.

Engine Stalling

This is likely to happen while you’re driving at high speeds, going up an incline, and similar other scenarios where your engine will need more fuel. Unless you want your car to suddenly stall while you’re in the middle of traffic, you should replace your dirty fuel filter as soon as possible.

Poor Fuel Economy

Poor fuel economy is another one of the most common signs of a bad fuel filter. When the engine doesn’t receive enough fuel, the powertrain control module (PCM) increases the fuel input to compensate. This causes the engine to burn more fuel than necessary.

Strong Gas Odors

Have you smelled anything unusual lately, such as a strong gas odor? If the answer’s yes, then you might be dealing with a dirty fuel filter. When it prevents fuel from reaching the engine, all that unburnt fuel escapes through the exhaust system. This can cause your cabin to smell strongly like gas.

In some cases, a strong gas odor can also point to a fuel leak or other issues in the fuel system. Whatever it is, it’s important to bring your vehicle to a mechanic as soon as possible.

Fuel Pump Noise

As its name suggests, the fuel pump pumps gas from the fuel tank to the injector or carburetor. A dirty fuel filter forces it to work harder to supply enough gas to the engine, and all that extra strain causes the pump to make noise. If this goes on for too long, the added stress can also cause the fuel pump to fail.

Illuminated Check Engine Light

A dirty fuel filter is also likely to trigger the check engine light on your dashboard. Low fuel pressure, an increase in emissions, and other similar issues are all red flags to your PCM. As soon as it detects any of these issues, it’ll turn on the check engine light to warn you.

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What Is a Fuel Filter For?

A fuel filter is specifically designed to prevent natural impurities, debris, and other contaminants found in gas from entering the fuel system. All that dirt can damage components such as the fuel injectors and cause the entire fuel system to fail.

What Causes a Clogged Fuel Filter?

As the fuel filter does its job, it’ll naturally collect many contaminants over time. This is why most manufacturers recommend replacing the fuel filter every 20,000 to 150,000 miles. Unfortunately, some people might forget to replace their fuel filter, causing the particles to clog the filter and prevent it from doing its job.

How To Check Your Fuel Filter

The best way to check your fuel filter is to ask a mechanic for help. However, if you’re confident in your skills, consider these helpful tips on how to tell if your fuel filter is bad:

  • Drain as much gas as possible out of the fuel filter.
  • Thoroughly clean the inlet to the fuel filter with a towel.
  • Lay another towel on your workbench before gently blowing into the inlet for an easier cleanup.
  • Allow the towels to dry outside or in a well-ventilated area before throwing them away.

If you blow into the inlet and find that no air is passing through, then the filter is likely clogged and needs replacing.

How Much Does a Fuel Filter Change Cost?

The exact cost will vary depending on several factors, such as your vehicle’s year, make, and model. However, the average cost of replacing a fuel filter ranges from $90 to $142, including labor. If you plan to replace it yourself, you can expect to spend anywhere between $10 and $920.

Other Filters in Your Car That You Should Inspect

When you bring your car in for its regular maintenance, your mechanic will also check if other filters need replacing. Here are other filters you should also inspect:

Engine Air Filter

As its name suggests, the engine air filter captures dust and other contaminants in the air that could damage the engine.

Transmission Filter

Automatic transmissions come with a filter that keeps dirt and other debris from entering and harming the hydraulic system.

Cabin Air Filter

This allows you and your passengers to breathe clean air by filtering dust, pollen, and other particles from the air before they can enter the cabin through the vents.

Written By CarParts.com Research Team

Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.