Skip the auto shop - Our mechanics make house calls
  1. Home
  2. Articles
  3. Symptoms of a Bad or Failing Fuel Filter (Auxiliary)

Symptoms of a Bad or Failing Fuel Filter (Auxiliary)

fuel filter

Virtually all vehicles equipped with gasoline engines are equipped with fuel filters that are meant to filter out any dirt or debris that could contaminate the fuel system or damage the components, and possibly even the engine. Some vehicles will come equipped with a second fuel filter, known as the auxiliary fuel filter, that serves as an additional filter to further protect the fuel system components and engine. When the filter becomes excessively dirty or clogged, it can cause issues engine performance issues. As the auxiliary fuel filter functions in the same manner as the primary fuel filter, the symptoms associated with it when it fails are similar to that of a regular fuel filter. Usually a bad or failing fuel filter will produce a few symptoms that can alert the driver of a problem.

1. Car is hard to start

One of the first symptoms of a problem with the auxiliary fuel filter is hard starting. If the filter becomes excessively dirty or clogged it may restrict fuel pressure or flow, which may cause the vehicle to experience difficulty starting. The problem may especially noticeable at cold starts, or after the vehicle has been allowed to sit for a while.

2. Engine misfires or decrease in power, acceleration, and fuel efficiency

Engine performance issues are another symptom of a problem with the auxiliary fuel filter. If the fuel filter becomes excessively dirty to the point of seriously restricting the flow of fuel, it may cause the vehicle to experience drivability issues such as misfires, a decrease in power and acceleration, poor fuel economy, and even stalling. The symptoms will usually continue to get worse until the vehicle can no longer run, or start.

3. Check Engine Light comes on

An illuminated Check Engine Light is another possible symptom of a faulty auxiliary fuel filter. Some vehicles come equipped with fuel pressure sensors that monitor the pressure and flow of the fuel system. If the fuel filter becomes excessively dirty and restricts the flow of fuel, and it is detected by the sensor, the computer will set off the Check Engine Light to alert the driver of a potential issue. The Check Engine Light can also be set off by a wide variety of other issues, so having the computer scanned for trouble codes is highly recommended.

While they are not found on all vehicles, auxiliary fuel filters are another important routine maintenance component that should be changed at the recommended intervals in order to keep the engine running in proper order. If you suspect that your auxiliary fuel filter may be having an issue, have the vehicle inspected by a professional technician, such as one from YourMechanic, to determine if the filter should be replaced.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Still not sure about your car's issue?
Diagnose your car
What kind of issue are you experiencing?
Brakes are squeaking
Car is not starting
Car is overheating
Car is shaking (vibrating)
Fluids are leaking
Heating and A/C
Smoke or steam is coming out of the car
Warning light is on
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

How Long Does a Throttle Return Spring Last?
Not all vehicles on the road feature an electronic throttle control (ETC), which is also called drive-by-wire. For vehicles that don't offer this system, they have a throttle cable instead that...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
Veteran and Military Driver Laws and Benefits in New Mexico
The state of New Mexico offers a number of benefits and perks for those Americans who have either served in an Armed Forces branch...


Related questions

Q: Toyota Yaris 1.0 VVTi GS problem starting at normal temprature

The most likely common problem with these symptoms is a sticky/dirty idle air control valve, which either needs to be cleaned or replaced. Other possibilities is a clogged fuel filter, failing fuel pump relay, or fuel pump itself. I would...

Q: Changing transmission fluid in 2005 Hyundai Sonata Common repairs on Hyundai Sonata

You've only got 40,000 miles on it and it's 2005--it's old. So, I'd say change the fluid and filter and use the factory fluid. Because the most common problem on those cars are bad transmissions, you don't want to chance...

Q: engine misfire. 1995 Toyota Corolla

Hello. These types of issues can be hard to diagnose. Most of the time they are caused by a failure within the distributor itself. Also common is the shaft being slightly worn, which will cause the RPM reading to be...