What Are the Symptoms of a Dirty Fuel Filter in a Car?

Updated April 17, 2017

A car's fuel filter screens out dirt and impurities from the gasoline or diesel so the impurities don't reach the fuel injector and fuel pump. A tiny piece of rust or debris can damage the fuel injector and ruin a fuel pump. Some car manufacturers recommend changing fuel filters every five years or 50,000 miles. Many mechanics disagree, advising consumers to clean and change filters more often to maintain engine life. A basic understanding of the car's fuel system makes it easier to spot symptoms and identify the possible causes of trouble.

Anatomy of the Fuel System

The fuel tank holds gasoline or diesel fuel. A fuel pump might be inside the tank, mounted to the engine or positioned on the frame rail. The filter strains the fuel before it reaches the fuel injector. A computer controls the mixture of fuel and opens the injectors, sending fuel to the engine. Fuel injectors have tiny holes which clog easily. A filter is necessary to prevent this from happening.

Failure To Start

Failing to start is one of the most common symptoms of a dirty fuel filter. If the ignition turns over but the car simply refuses to start at all, the fuel filter might be clogged. If the engine does turn over but takes a long time to do it, this could mean the filter is partially blocked. If the filter is not cleaned or replaced, the fuel pump and fuel injector will be affected and might have to be replaced

Engine Stalls

If you stop at a traffic signal and the car stalls, the problem could be a clogged fuel filter. The same thing could happen when driving up an incline or on a steep slope. The car might hesitate and then come to a jerky stop, just as it would when it's running out of gas. A clogged fuel filter is preventing the engine from getting enough gas, causing the stall.

Engine Has Decreased Power

An engine might respond sluggishly when the driver steps on the gas, or it might fail to accelerate at all. This is a sign that the engine is not getting enough fuel to pick up speed.

Engine Misfires Or Idles Roughly

If the engine knocks, rattles, shakes or otherwise behaves erratically, it might not be getting enough fuel to operate smoothly and maintain a steady speed. Coughing and jerking are symptoms that the engine is starved for gasoline. Tiny particles can block the small openings in the fuel injector. The fuel filter should be cleaned or replaced before the fuel injector is damaged.

Engine Hesitates

The car starts but doesn't accelerate smoothly. Once the ignition turns over, the car balks, lurches or hiccups along instead of picking up speed. Its performance is erratic and the hiccoughing starts unexpectedly. You might smell a strong exhaust odour after these balking and coughing episodes.

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About the Author

Nancy Williams has been writing about health-related topics since 1979. Her work has been published in "Prevention," "Nurseweek" and "Senior Life." Williams is a registered nurse with more than 35 years of experience and holds a Bachelor of Science degree in health-care administration. She is working on a book about historic sites in the West.