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How to Tell if You Have a Clogged Fuel Filter 

Do I Need to Replace My Fuel Filter

Every vehicle that runs on gasoline has to have a fuel filter installed somewhere along the fuel line. This could be located along the lines under your vehicle, in the fuel tank itself where it connects to the fuel lines, or just before where the fuel enters your engine. Regardless of where it is, all fuel filters have the same job. Because your gasoline, your fuel tank, and the fuel lines can become contaminated with dirt and debris, the fuel filter is there to ensure that only clean gasoline makes it to your fuel  injectors to be combined with air in your combustion chamber and ignited to power your vehicle.

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The filter itself is about the size of a small can usually and is just a paper filter inside much like the filter that your coffee maker at home uses. Gasoline passes through the paper and any grit and debris is caught on the surface while the clean fuel is able to continue on down the line.


What Causes a Clogged Fuel Filter?


Obviously a fuel filter is going to be contaminated by any debris, grit, or other foreign matter that is present in the gasoline you put in your car.  One of the most common ways to clog a fuel filter is by allowing your gas tank to run out while you're driving. The closer you get to the bottom of the tank, the more contaminated fuel you're going to be pumping through the system. Any debris at the bottom of your tank is going to be sucked up into the line and will catch in the filter to clog it faster than you would normally expect it to. For that reason, you never want to let your fuel tank run too low, too often. 


The more clogged that your fuel filter is, the more damage you're going to cause the rest of your car. It will throw off the pressure in your fuel lines and cause your fuel pump to work harder to try to pump the fuel to the injectors. That will put undue strain on the pump until such time as it breaks down, which could be a costly repair job for you to deal with. Getting a fuel pump repaired could cost you anywhere from about $300 to well over $1,000 depending on the make and model of your vehicle. For that reason alone, it's a good idea to maintain your fuel filter and be sure it's clean and working properly whenever you can.


 Now that you know what your fuel filter does and how it can get clogged, it would be helpful to know a few ways to identify if your fuel filter is clogged or not. That way you can fix the problem before it goes from bad to worse and keep your car and other parts of your engine working properly.


 What Does a Bad Fuel Filter Sound Like?


As with many problems in your vehicle, a bad fuel filter is going to change the way your car sounds while it's running. Because a clogged fuel filter is going to alter the pressure in your fuel lines and  therefore potentially cause a drop in engine pressure as well, you may notice a distinct knocking or ticking sound when you're driving as a result of that bad fuel filter. This will happen once the vehicle is warmed up a bit and will continue for the duration while your vehicle is driving. There are a handful of other problems that can occur in a car that will make a similar symptom, and even a handful of problems that will cause the pressure to be imbalanced in your  engine as well so you may need to rely on several different symptoms to coincide with this one to be sure that it's actually your filter causing the trouble. 


Will a Clogged Fuel Filter Cause a Loss of Power?


Another sign that your fuel filter is potentially going bad could be a loss of power in your vehicle. This is because the flow of fuel has been so badly compromised due to the clog in your fuel filter that it's not able to reach the engine either in the correct volume or at the correct time to allow for the proper combustion reaction to take place. This means that you are going to be dealing with a significant loss of power as a result.


What are Some Other Symptoms of a Bad Fuel Filter?


Aside from what we've mentioned, there are a handful of other things that you can be on the lookout for that will let you know if you have a clogged fuel filter or not.


Bad Gas Mileage: When a clog in your fuel filter prevents the correct flow of fuel from the tank to the engine, your fuel pump is going to try to compensate by working harder. Your engine will require more fuel to make up for what's missing and your fuel pump will try to accommodate. That means it will be aggressively pumping fuel towards your engine even though you don't actually need as much as it's trying to pump because it's the clog causing the problem. This can result in fuel not burning correctly and essentially being wasted as it sprays into the combustion chamber but does not ignite. The result will be that not only are you experiencing a loss of power and poor performance, but you're going to be having to fill up at the gas pumps more often as well.


Rough Idling: Another common symptom of a bad fuel  filter is when your vehicle is idling roughly or erratically. You'll notice the engine sounds louder than normal and it will seem like your vehicle is jerking and stuttering even when you're simply sitting still in it. This is consistent with not having the correct amount of fuel burning in the combustion chamber of your engine.


Misfires:  You’ll notice this happening especially when you are trying to accelerate and your engine either stalls or suffers a misfire which causes a loss of power in your vehicle. When you're putting your foot on the gas to try to pick up speed the opposite reaction will happen. Your engine may actually die on you completely because you're unable to transmit the correct amount of fuel into the combustion chamber so the combustion reaction doesn't happen the way it's supposed to, or it will not even happen at all. 


Car Won't Start:  If the clog in your fuel filter is bad enough it will prevent the adequate flow of fuel from reaching your engine at all. That means that even when you turn your key in the ignition you'll hear your vehicle trying to start but because the clog is so severe no fuel can reach the combustion chamber so your spark will have nothing to ignite in the first place. 


The Smell of Fuel:  You should never be able to smell gasoline in the cabin of your vehicle at any point in time. If you are smelling a gas smell in your vehicle it means that you likely have a leak somewhere which could be particularly dangerous. The first thing you'd want to check is your gas cap itself just to make sure it's secure in place because that is the likely source of a gasoline odour. However, if that's not the case then a fuel filter that is so badly clogged there is a leak around it is a potential cause. This is not the most common symptom of a clogged fuel filter by any means, but it is a possibility.


If you do smell gasoline at any point in time, you definitely do not want to let this go until you figure out what it is. You need to get to a mechanic as soon as you can. Aside from the cost of losing gasoline the danger of a gas leak is extremely severe. Not only do you risk fire, even the fumes themselves entering your vehicle while you're driving can lead to nausea and lightheadedness which could cause an accident. So, remember, anytime you smell gasoline in the cabin of your vehicle, open your windows to allow the fumes to dissipate and get to a mechanic as soon as you can.


When Do You Need to Replace Your Fuel Filter?


Your vehicle’s manufacturer will likely have listed in the owner's manual the recommended time for changing your fuel filter. Like oil filters, timing belts, and many other parts of your vehicle it's subject to a routine schedule of maintenance that you should follow if you want to keep your car running at its best.


This will depend on the specific make and model of your vehicle of course because it does change significantly from one vehicle to another. For instance, while the average used to be between 40,000 miles and 80,000 miles, Mercedes-Benz suggests that you can wait a hundred fifty thousand miles before swapping out the fuel filter in one of their vehicles and some models of Toyota suggest you don't need to change the fuel filter out ever. In older vehicles you may need to change it out as often as every 20,000 miles.  Ford trucks that have diesel engines recommended that the fuel filter be changed every 15,000 miles. So, it really does depend, and your best bet is to always defer to what the owner's manual of your specific make and model suggests.


 Of course, if you're experiencing any of the symptoms we've lifted that indicate your fuel filter has gone bad you don't want to wait longer than necessary and you should make the change sooner rather than later if there's evidence that your fuel filter does in fact have a clog in it.


How Much Does It Cost to Fix a Clogged Fuel Filter?


The cost of a replacement fuel filter is not particularly high. You can buy a brand new fuel filter from a site like autozone.com for as little as $2 to as much as about $100. Taking it to a mechanic to get the fuel filter changed for you will therefore cost likely anywhere from about $50 to $200 depending on the mechanic you take it to. The whole job should only take around an hour so you can gauge from there what labour costs and material costs are going to break down as, depending on the kind of fuel filter you get.


It's also possible to swap out the fuel filter by yourself rather than taking it into a mechanic to get the job done. As we said earlier, the location of your fuel filter is not consistent from one vehicle model to another so you're going to need to check your owner's manual to find out exactly where it is in order to determine how best to replace your fuel filter. Some of them you might find in the engine bay of your vehicle while others will require you to get the car up on jack stands so you can access the fuel lines from underneath. Fortunately, there are a number of videos online that can walk you through the process of swapping out the fuel filter in a vehicle, and you may be able to even find some that are specific to your particular make and model to make it that much easier for you. You'll have to do some searching to find out for sure.


The Bottom Line


Even though a fuel filter may only cost $2 and is essentially just some pieces of paper held inside of a metal container, when it goes wrong you can see just how catastrophically bad your car could potentially fail on you as a result. Sometimes the simplest things are the most important, and also, they are very easy to overlook. Make sure you know how long the fuel filter in your car is meant to last and keep track of how long it's going to be until you need to swap it out. That way you can avoid any of the major problems associated with a bad fuel filter and keep driving your car as normal.


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