Symptoms of a Bad or Failing Fuel Filter (Auxiliary)

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.


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Kenneth

20 years of experience
775 reviews
Kenneth
20 years of experience
BMW X5 L6-3.0L - Fuel System - Rancho Palos Verdes, California
Kenneth was extremely knowledgeable. He correctly diagnosed my vehicle by actually going under the hood, removing a section and running some sort of test that told him exactly what the problem was. He also arrived 15 minutes early and had prepared for the visit by contacting me the day prior to get further clarification.
Porsche Cayenne - Car Battery Replacement - Pasadena, California
Kenneth is HIGHLY recommended - I have always taken my Porsche to the dealer for service and needed a new battery replacement ASAP. None of the national auto service chains would do the installation and the local specialist charged the same as the dealer - so I decided to give YourMechanic a try. Not only did I get it taken care of the next day, Kenneth showed up at my place and knew exactly what to do... and close to 1/2 the cost the dealer charged!?! I will never worry or dread getting my car serviced, repaired, or just a simple checkup again!

Michael

21 years of experience
244 reviews
Michael
21 years of experience
Chrysler 300 V8-5.7L - Exterior Door Handle Replacement (Driver Side Rear) - Riverside, California
On time and quick.
Suzuki XL-7 - Power Steering Pump - Moreno Valley, California
Mike accepted the job at the last minute scheduling on a Holiday Weekend. He is dedicated to his job, showed up on time and carried himself in a professional matter at all times. Thank you for the hard work!

Michael

4 years of experience
230 reviews
Michael
4 years of experience
Volkswagen Jetta L5-2.5L - Fuel System Inspection - Indianapolis, Indiana
professional ,informative and knowledgeable

Raymond

37 years of experience
402 reviews
Raymond
37 years of experience
Chevrolet Impala V6-3.4L - Fuel System - Las Vegas, Nevada
Raymond was very knowledgeable mechanic and through in his testing. I trust him for any future from your mechanic.

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