When thinking of car maintenance, engine air filters, spark plugs, and oil changes are the most frequent tasks that usually come to mind. One replacement item that is rarely thought of is the fuel filter. It usually isn’t until an engine starts to perform poorly that most vehicle owners start to pay more attention to the fuel filter. Like the other filters in the car, the fuel filter is extremely important as it keeps your engine running clean!
Function of a Fuel Filter
The function of the fuel filter is to screen out dirt, rust, and any contaminants in your fuel system before they are carried to your fuel injectors or carburetor. Both fuel injectors and carburetors are extremely sensitive to contaminants as unfiltered contaminants can build up, causing the nozzles that deliver fuel to get stuck either open or closed. This would quickly lead to over-fueling or under-fueling which can cause damage to the fuel system or other engine components.
Fuel filters are typically cylindrical with an inlet and an outlet port. Fuel hoses are connected to both the output and the input, forcing all fuel through the filter before it is delivered to your engine. As fuel passes through the filter, the filter element traps particles while allowing fuel to pass through. This is true whether you drive a diesel or gasoline vehicle. Fuel filters are commonly found under the hood in the engine bay or underneath the car near the fuel tank.
Common Symptoms of a Bad Fuel Filter
As with any filter, most of the associated issues are related to reduced flow over time. Most of the issues with fuel filters will present themselves in one of the following ways:
Loss of Power – Your engine runs on fuel, and less available fuel on account of a clogged fuel filter means less power. You’ll notice engine performance is reduced meaning slower acceleration and more throttle required to make it up hills.
No-Start Issues – With a severely dirty filter, fuel delivery can be reduced to the point where the engine won’t run at all. In this case, as you crank your car’s starter, your engine may sputter a bit but will fail to start. This is most typically seen when trying to start cars after long periods of sitting as rust can build up and flake off the inside of the fuel tank which leads to filter clogs.
Misfiring – A dirty filter can reduce the correct amount of fuel to the engine and that will cause a lean running condition (too much air, not enough fuel). You may notice that the engine idle is rough or that the car momentarily hesitates as you accelerate.
Canister or Filter is Leaking – In older cars that have sat for a period of time, the steel canister that makes up the filter body can start to rust. If it degrades to the point that the body of the filter leaks, it’s time to grab a new one and replace it. It should be noted that leaking fuel can cause an extreme fire hazard, so if this is the case it must be addressed promptly.
Reduced Gas Mileage – A clogged filter is going to cause your engine to underperform. Your gas mileage will suffer and you’ll find that you are getting fewer miles per tank causing you to hit the gas station more often.
Replacing a Fuel Filter
A dirty fuel filter can cause enough restriction to put excess pressure on the fuel pump and cause it to fail over time. Similarly, it can cause other fuel system components to fail such as fuel injectors. Beyond causing damage to the fuel system, a continued lean running condition can also cause damage to your engine.
Note: The example steps below are intended for general informational purposes solely to help give you an idea of project difficulty and tools required. As all cars are engineered differently, repair procedures and safety hazards vary from vehicle to vehicle. To ensure that you have a vehicle specific repair procedure and an exhaustive list of potential safety hazards, we advise you reference a factory service manual for your vehicle. Similarly, referencing a repair manual such as Chilton or Haynes might serve as a less expensive alternative.
Step 1 – Take appropriate safety precautions. Depending on your vehicle, you may be working with fluid under pressure. Similarly, fuel is flammable. Ensure that you are wearing appropriate protective equipment, such as safety glasses to avoid eye injury. Also, ensure that you are working in a well ventilated space. Fuel vapors can accumulate in closed spaces such as garages which can create a significant fire hazard.
Step 2 – Understand what type of vehicle you are working on. If you’re working on a carbureted vehicle, the fuel system typically has relatively low pressure in the fuel lines when the vehicle is turned off, although it’s still a good idea to clear the lines of fuel pressure prior to starting work as a safety precaution. A fuel injected vehicle may have significantly higher residual pressure in the lines. For these systems, you typically need to disable the fuel pump to reduce the pressure and then empty the fuel lines. Often times this can be accomplished by removing the fuse for the fuel pump and running the engine until it runs out of fuel (which is limited to what is in the lines since the pump won’t deliver new fuel if it’s disabled), however check your vehicle owner’s manual to ensure that you are taking the correct safety precautions for your vehicle as high pressure fluids can be extremely dangerous.
Step 3 – Determine where the fuel filter is located on the vehicle. It will typically be on the high pressure side of the fuel lines. If it is under your car, you will need to raise your vehicle using a floor jack and support it with jack stands. Once you locate the filter and have ensured that pressure has been bled from the fuel system, you need to disconnect it from the fuel lines. The filter may be connected with hose clamps or QD (quick-disconnect) fittings depending on the vehicle. For hose clamps, a small screwdriver is usually the correct tool to get them off. For QD fittings, these can often times be removed by hand.
Step 4 – With the fuel lines disconnected, you can now remove the filter from the vehicle. It usually has a bracket holding it in place on the vehicle. That bracket may have additional fasteners to remove to allow the filter to be taken out of the vehicle. Typically a screwdriver or a socket & ratchet set will be required to remove these fasteners.
Step 5 – With the old filter taken off, you can install the new filter. The filter should have an indicating arrow or mark depicting the correct direction that the fuel needs to flow through the filter. Make sure you install using the correct orientation.
Step 6 – With the new filter connected to the fuel lines, you can reinstall the bracket that holds the filter in the vehicle. Again use the screwdriver or socket & ratchet as needed.
Step 7 – Replace the fuse you removed to stop the fuel pump from running. With the vehicle parked, you can start the engine and check that there are no leaks at the filter. If any leaks are present, stop the engine immediately and repair the leak. If no leak is found, you can take the vehicle on a short test drive to ensure your vehicle runs correctly.
Best Fuel Filter Brands
When it comes to selecting the best replacement fuel filter for your vehicle, there are many brands out there to pick from. To help narrow your search, we have provided three brands that we highly recommend as we have found them to be a good balance of quality and value over the years we have been working on cars.
Fram has a large fuel filter product selection, and you’ll recognize their boxes as the bright orange ones. They have a large distribution network that provides replacement filters through local and online retailers. Cost is on the lower end and quality is consistent which means Fram provides great value for replacement fuel filters. We have used many Fram filters over the years and have never had any issue to speak of.
Hastings has a large catalog of replacement filters covering most vehicles. They offer air, oil, and fuel filters to keep your vehicle running with optimum performance. They make a variety of great filters, and their fuel filters are no exception. Pricing is in the middle of the range but the quality is very high so we are still comfortable recommending Hastings as a high value fuel filter manufacturer. Overall, we think you’ll be satisfied if you choose to get a Hastings filter.
AC Delco has a large selection of filters specific to General Motors vehicles. They provide good quality at a moderate price for most General Motors vehicle brands (Chevrolet, Cadillac, etc). While AC Delco is probably most well known for their ignition components, they are also pretty big players when it comes to fuel system components which makes them worth checking out.