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How to Tell if your Fuel Filter Is Bad

Nidhi Nangia
By Nidhi Nangia. Updated: March 23, 2017
How to Tell if your Fuel Filter Is Bad

The fuel filter in your car is responsible from keeping your engine clear from dirt and debris. This is because they can enter when you open the cap for the fuel tank to pump gas. It is unlikely large pieces of dirt will enter the tank, but even small amounts of sediment which build up from the fuel itself need to be removed. If they aren't, they can cause the fuel pump and injectors to wear down or clog as the particles get into the system. The fuel filter collects these particles, usually in a concertina shape made from paper. You will need to see how to tell if your fuel filter is bad to make sure you don't have problems down the line, so keep reading oneHOWTO and see how it's done.

You may also be interested in: How to Clean Your Fuel Filter
  1. The engine starts with difficulty
  2. The engine stops frequently
  3. Problem with the acceleration
  4. Look at your exhaust fume
  5. Improper idling
  6. Sputtering

The engine starts with difficulty

Normally, this is a major sign which indicates that your fuel filter is bad. When you turn the key (or press the button) in the ignition, the car may stall a few times before starting. It may not even start at all. The fuel filter may be so clogged that the fuel doesn't even reach the engine at all. If this happens there is no fuel to combust and the engine won't start. If it take a few attempts, and then starts, it might be because the fuel filter is not completely saturated but still needs cleaned.

There are other reasons for the ignition not working immediately or at all. The battery may be dead or suffering from a loose connection. If all you hear is a "click" sound rather, this is probably the case. It could be something to do with the ignition itself or even the steering lock.

How to Tell if your Fuel Filter Is Bad - The engine starts with difficulty

The engine stops frequently

Even if your car starts, it may stop abruptly while running, especially when you're driving up a steep slope. This indicates that sufficient fuel is not reaching the car's engine to keep operating, thus causing the engine to stall frequently. This is particularly the case if the fuel filter becomes more clogged by new debris in the tank. One of the main reasons your fuel filter becomes so clogged comes from driving the car on empty (i.e. when the red "no fuel" light is lit on the dashboard). This is because dirt and sediment falls down to the bottom and the fuel pump has greater access to it. Ensure you fill up as soon as this light comes on. Better yet, don't let your fuel go down so low that this happens in the first place.

Problem with the acceleration

Sometimes, the engine may start, but it may not accelerate. It might behave funny when you try to press down the accelerator. Sometimes, it may even suffer from slow-down syndrome when you drive at a certain speed. This happens because the engine is not getting enough fuel to run any faster. If that’s the case, no matter how hard you step on the accelerator, the speed does not increase and it remains the same. This period will not usually last very long as it will soon start to stall or not even move at all.

How to Tell if your Fuel Filter Is Bad - Problem with the acceleration

Look at your exhaust fume

The exhaust fume coming from your car’s engine may appear cloudy and dark. This indicates that your fuel filter needs cleaning or replacement. You may sense an awful smell coming from your exhaust, which is a sign that your fuel filter is dirty and clogged. It will need to be checked. Frequent misfire may also indicate improper functioning of your fuel filter.

There are other reasons smoke may emanate from your exhaust. It could be a problem with leaking anti-freeze or coolant. If the smoke is thick and white, this could be a little more serious like a problem with the piston or cracked gasket. If this is the case you should take it to the mechanic immediately as it may be dangerous to drive.

How to Tell if your Fuel Filter Is Bad - Look at your exhaust fume

Improper idling

Another symptom of a bad fuel filter is the vehicle jerking or making a stutter sound when idling. This indicates that the car’s engine gets enough fuel while running, but it is inadequate when it has to idle. This is because the fuel filter is not clean enough to deliver an easy idle.

How to Tell if your Fuel Filter Is Bad - Improper idling


Sometimes, your car may sputter when you drive it at low speed or under conditions when the fuel filter has minimal blockage. This indicates the starting of the fuel filter getting clogged, but if you neglect it, you may need to replace it entirely. So, if you experience any such sputtering, it is better to take it as a first sign of bad fuel filter, and get it corrected immediately.

How to Tell if your Fuel Filter Is Bad - Sputtering

If you need to check your fuel filter, there are ways to do it. You will need to take it out from its casing and look to see what type it is. Some of them have a clear plastic cover. From this you'll be able to see how clean or dirty the filter is. The concertinaed paper filter often comes in a pale yellow or cream color. If you see that it is darkened and dirty, then it will be obvious that your fuel filter is bad. However, if you have the more likely opaque filet, you will need to take it out and look at it.

One way to check if it is bad is to blow air through from one end to the other. If there is an accumulation of dirt, you will see black mess come out from the opposite end. A similar trick is to take it out and bash the end of it on a soft surface. Don't bash too hard or you may break it. If it is dirty, you will see the gunk come out of it. Don't do it on a hard surface even if you tap gently. This is because if you do it near anything with the possibility of sparking, you can end up igniting the fuel still in the filter.

If you want to read similar articles to How to Tell if your Fuel Filter Is Bad, we recommend you visit our Car Maintenance and Repair category.

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Edward Wilburn
My car is losing power while driving. And at times at low speeds it cuts off but starts right back with no problem.
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How to Tell if your Fuel Filter Is Bad