Clogged Fuel Filter Symptoms

Clogged fuel filter symptoms generally show up as hesitation or sputtering when you press the gas. This happens when the filter gets too clogged to pass fuel through to the engine.

Don't rely on these symptoms to tell you if a fuel filter is dirty, however. Some fuel filters have a bypass mechanism that lets fuel go straight from the gas tank to the engine if the filter gets clogged. That allows any impurities in your vehicle's fuel to attack the carburetor or fuel injection system directly, where they can cause expensive damage.

Preventive Maintenance
Fuel filters should be changed every 30,000 miles, otherwise they will clog and cause problems with the vehicle starting or running properly. Fuel filters are normally located about halfway between the front tires and the rear tires, and are mounted to the frame rail of the vehicle. On some vehicles, the fuel filter is located near or on the firewall in the engine compartment.

You may notice some or all of the following symptoms of a clogged fuel filter:

• The vehicle does not start. The fuel filter is clogged and does not allow enough fuel through the lines to turn the engine over.
• The vehicle starts, but does not idle properly. The fuel filter is clogged. It allows enough fuel through the lines to run the engine, but not enough fuel is getting through to keep the vehicle idling. The vehicle may drive, but it will be sluggish and may stutter or stall.
• The vehicle starts and idles properly, but when trying to drive, the vehicle jerks. The fuel filter is clogged just enough to deny the carburetor or fuel injectors the proper amount of fuel. The engine is starved for fuel and stutters and jerks at higher speeds.

Check Engine Soon
If your vehicle is fuel injected, a clogged fuel filter denies the vehicle the proper 14.5:1 air-and-fuel mixture. The mixture it has is lean, which means there is too much air for the amount of fuel going through the system. The computer sees this via the oxygen sensors and will turn the check engine light on. When checked, the code will show that one or more of the oxygen sensors have a lean reading.

A lean reading is also caused by a bad fuel injector, a bad plug, a bad plug wire or a faulty oxygen sensor. All ignition components and fuel components should be checked before condemning the oxygen sensor. Start with the fuel filter, particularly if the problem is new. Replacing the filter could be all that it takes to get the Check Engine light to turn off. If the Check Engine light has been on for a while, you could be looking at a more costly problem involving the injectors themselves.