How to Check a Fuel Filter

by Cassandra Tribe

If your car seems to be losing power or begins to stall out, especially when you press the accelerator, you may have a problem with your fuel filter. Fuel filters are one of the easiest car parts to check and to replace as well. Even better, most in-line fuel filters are inexpensive. You will need someone to help you do this, one person will have to turn the ignition on while the other observes how the fuel delivery behaves at different points during these steps.

Locate your fuel filter. On most cars it will be in line (placed between two sections of the fuel line), usually under the car near the fuel tank. It will look like a small cylinder. Some cars use an in-line filter that is located in the engine compartment.

Look at the condition of the paper filter inside, if possible. Some cars use a see-through plastic fuel filter, and you can see the actual paper filter inside. If it is a dark brown (not tan or golden brown) or you can see any sediment in the gas trapped in the filter, then you need to replace it. Other filters are sealed steel cylinders that you cannot see into.

Loosen the hose clamp on the fuel line that goes into the fuel filter from the gas tank by using a flat-head screwdriver to turn the clamp screw counter-clockwise several times . Hold the fuel filter so it is tilted up slightly, and pull the fuel line off. This way the gas in the filter will not spill out.

Put the end of the fuel filter over a glass jar. Have your helper engage the emergency brake of the car and place it into neutral. Then, have them put the key into the ignition and turn it to the first position. You do not want them to turn the engine on, just to connect the power to the fuel pump. Watch the rate at which the gas comes out of the fuel line into the jar. Have your helper turn off the ignition, and reconnect the fuel line to the fuel filter.

Loosen the hose clamp on the fuel line that comes from the fuel filter and goes to the engine (the same way you did in Step 3). Hold the hose at a slightly upward angle and pull the filter from the hose. This will help prevent gas in the line from spilling out.

Hold the end of the fuel filter over the glass jar and have your helper turn the ignition to the first position again. Watch the rate that the gas comes out of the fuel filter. If it is even slightly slower than the rate at which the gas flowed from the line directly off the tank, you filter is dirty and you need to install a new one. Reconnect the filter to the fuel line so gas or vapors do not continue to leak out, and purchase a new filter to install.

Tip

  • check If you have replaced your fuel filter because it was dirty and your car stalls again, replace your fuel lines, as the debris in the filter most likely represented only a small portion of what is in your lines and still clogging them.

Warning

  • close Do not smoke or operate any kind of open flame near the vehicle while you are testing the fuel filter. The vapors from gasoline are as flammable as the gasoline itself.

Items you will need

References

About the Author

Cassandra Tribe has worked in the construction field for over 17 years and has experience in a variety of mechanical, scientific, automotive and mathematical forms. She has been writing and editing for over 10 years. Her areas of interest include culture and society, automotive, computers, business, the Internet, science and structural engineering and implementation.