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How Do I Know If I Need to Replace My Fuel Filter?

Fuel filters are a small but important component in your GM vehicle's fuel system. Fuel filters prevent any contaminants from reaching your engine. Occasionally they get clogged and need to be replaced. While the size and location of the fuel filter vary from one vehicle to the next, the symptoms of a clogged fuel filter are the same.

In this article we'll cover the following:

  • What is a fuel filter?
  • Signs of a bad fuel filter
  • How to diagnose a bad fuel filter
  • Replacing a fuel filter

What Is a Fuel Filter?

OEM GM Fuel filter

A fuel filter is a small filter that prevents contaminants in the fuel line or fuel tank from reaching the engine. The size, number, and location of the fuel filter vary depending on the make and model of the vehicle. Some cars have more than one filter - typically one in the fuel tank and another in the fuel line. Many modern vehicles just have one filter built into the fuel pump.

Signs of a Bad Fuel Filter

Symptoms of a bad fuel filter are similar to other fuel system issues and can include one or more of the following:

  • Vehicle stalling or losing power - The vehicle stalls or loses power either while idling or when you drive it.
  • Sputtering or random hesitation - Similar to stalling or losing power, the vehicle hesitates or sputters for a short period of time then acts normal.
  • Hard starting - The vehicle is hard to start, either taking longer to start or sputtering and struggling to start.
  • Backfiring or misfiring - You hear a backfire or the engine misfires. This symptom could occur independently or in addition to one of the other symptoms.
  • Fuel system component failure - Signs of a fuel system component failure include clogged or fouled fuel injectors, a noisy or malfunctioning fuel pump, or a clogged fuel line.

How to Diagnose a Bad Fuel Filter

GM fuel filter replacement

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The easiest way to diagnose a bad fuel filter that is located in the fuel line is to inspect it in one of the following ways:

  • If the fuel filter is in a transparent housing, you will see a yellow, tan, or light brown colored filter. If it's black, a dark shade of brown, looks clogged, or has gunk floating in it, then it's likely clogged.
  • If the fuel filter is in a solid metal housing, you can check it by doing one of the following.
    • Remove the downstream fuel line between the fuel filter and the engine. Then take a jar or small container and point the open end of the fuel filter into it. Next, have someone turn the ignition to the "on" position without starting the car. If the fuel pump engages, look at the fuel flow coming out of the filter. If trickles out, or is uneven or intermittent then the fuel filter is clogged.
    • Take the fuel filter off the car and thoroughly clean one end with a clean shop rag. Then use an air source, like an air compressor or air pump to blow air through the filter. If there's more than a minimal amount of resistance, it's likely the fuel filter is clogged. NOTE: Gasoline is flammable and toxic so use extreme caution with this method.
  • If the fuel filter housing is leaking, then the leak could be the source of your issues. In this case, you'll need to replace both the fuel filter and fuel filter housing to resolve the problem. This link shows how to diagnose a failing fuel filter housing.

If the filter is located in the fuel tank, you can attach a pressure gauge to the fuel line under the hood. If the pressure is lower than spec, either the fuel pump is going bad or the fuel filter is clogged. To repair either, you have to pull the pump assembly, which includes the filter, from the tank. In some cases, the manufacturer has put in an access panel so you can do the job without lowering the tank. This makes the job fairly easy. In other cases, the tank has to be lowered, which can take some time.

Replacing a Fuel Filter

Fortunately, fuel filters are inexpensive and easy to replace on most GM cars. The exception to this rule is if the fuel filter is built into the fuel pump or part of the fuel tank assembly. If you have questions about where to locate your fuel filter, what part you need, or how to replace it, just give us a call or contact us online.