Odds are if you’ve come to our website, you know the value of good vehicle maintenance. We’d also bet you perform certain maintenance items more frequently than the manufacturer tells you to. Or, you upgrade components with performance-oriented parts designed to last longer and do a more effective job. We understand completely.
One maintenance item that’s often overlooked is a vehicle’s fuel filter. Naturally, you’d assume these would get replaced on a schedule the same way an engine’s oil, oil filter, or air filter is. But owner manuals these days can be vague about replacement intervals, and non-car folks aren’t always aware they exist. The rub is that fuel filters are not easy to access - and even if they were, visual inspection would provide no indication of internal condition.
Even when replacing the fuel filter is a scheduled maintenance item on your vehicle, there are still reasons why a new one might be needed at other times. For example, maybe you purchased a car used with little or no documented maintenance history. Perhaps a previous owner, drawing a blank on what this maintenance item even is, might have guessed the fuel filter was replaced when it wasn’t. Or, somewhere along the way, an unscrupulous mechanic claimed to have put a new one in but didn’t. When a fuel filter gets dirty enough, there will be noticeable symptoms.
In the scope of this article, we’ll look at what a fuel filter is, why they need to be replaced, and how to recognize those symptoms telling you a new one is needed. All this is good knowledge to have if you’ve suffered any of the indignities mentioned in the paragraph above.
What Is A Fuel Filter?
To ensure all of the fuel reaching your engine is clean, it must pass through one (or two) filters specially designed to catch and hold any impurities present. “Impurities” can include sediment that collects at the bottom of a fuel tank over time. Sediment even affects brand new vehicles if they fill up from a gas station with an underground storage tank that’s recently been filled and effectively “stirred up”. Whether gunk in the fuel originates from sediment or poor quality gasoline doesn’t matter, it must be prevented from reaching the engine where it can cause real harm.
Cleaning the fuel that’s sent to the engine also keeps fuel injectors spraying at full force instead of becoming clogged up and ineffective.
Where Is A Fuel Filter Located?
The location of a fuel filter varies from vehicle to vehicle. On many newer cars and trucks, the filter is located in the fuel tank where it may or may not be part of an integrated fuel pump module assembly. Or, it may be mounted on the vehicle frame outside of the tank where it’s surrounded by a protective shield. Many vehicles are equipped with two filters – one inside the tank, and one outside the tank along the fuel line somewhere.
In some cases where the filter is inside the fuel tank, it may fall under the category of “non-serviceable” if it’s part of an integrated pump assembly. This means the pump contains a permanently-mounted filter element that’s not designed for regular replacement. Instead, it’s only replaced when and if a new fuel pump is installed.
However, some filters mounted in the top of the fuel tank are designed for easy replacement thanks to an access portal located below a removable rear passenger seat cushion. If you’re not sure which type of setup your vehicle has, the owners manual should clarify whether the filter is serviceable or not. For a better visualization of in-tank fuel filters, we invite you to read our related article How To Replace An In-Tank Fuel Sending Unit.
Diesel Fuel Filters
Typically, diesel-powered vehicles have two separate fuel filters: one in the tank, and the second often found in an underhood location. This second filter is specifically designed to remove water (extremely bad for diesel engines) and catch smaller impurities which would pose a problem for modern diesels engineered with cleaner-running, high-pressure fuel setups.
Since diesel fuel is thicker and less refined than gasoline, a more frequent replacement schedule may be listed by the manufacturer - some even specify every 15,000 to 20,000 miles. Because diesel fuel naturally contains more impurities, we recommend strict adherence to any vehicle maintenance schedule.
Vehicle Manufacturer Recommendations
Earlier, we mentioned today’s owner manuals often disregard fuel filter replacement entirely because the filter element is a permanent part of the pump housing. Looking at eight currently popular vehicles sold in the United States, replacement of fuel filters isn’t listed anywhere for gasoline-powered versions. Although two of those models, when equipped with available diesel engines, do specify replacing the fuel filters - one every 20,000 miles, and the other every 40,000 miles.
This is a far cry from vehicles produced decades ago which typically list fuel filter replacement as an across-the-board maintenance item every 30,000 to 40,000 miles. Vehicles built during the first decade or so after the turn of the millennium may have gone to higher intervals of 50,000 to 60,000 miles. This is due in part to better filter materials and refining advancements yielding cleaner fuels overall.
Signs Your Old Fuel Filter Needs Replacement
In the beginning stages of a clogged fuel filter, you’ll experience poor fuel mileage. As the problem worsens, symptoms typically manifest themselves in the form of hard starting, uneven idling, hesitation, and loss of power. Your engine might even run normally for a few blocks after starting, then bog down completely when more power is needed for an uphill grade or a highway on-ramp. Sputtering or stalling may occur.
Reduced or inconsistent fuel pressure resulting from clogged filters will be detected by modern engine management computers because of random cylinder misfires that occur as a result – usually when the engine is under load. If multiple misfires are present after enough on-off cycles of the key, the dreaded check engine light will come on. It’s important to note that spark plugs can also be fouled by these improper running conditions, so they may be a primary or secondary cause of the check engine light.
A scientific method that technicians use to check the condition of a fuel filter is to perform a fuel pressure test near the injectors at the fuel rail. The psi (pounds per square inch) reading measured after the fuel has gone through the filter is compared to what the normal specified psi should be for the vehicle. A significant amount of reduction can signify a clogged filter. If this occurs, fuel filters are replaced and the psi is re-checked to ensure the pump itself is operating properly.
When To Replace A Fuel Filter
Even with cleaner gasoline coming out of the pumps these days, we still recommend replacing fuel filters regularly on vehicles where it’s possible to do so. For newer cars and trucks, go with replacement every 60,000 miles – unless the manufacturer says to do it more frequently.
If the manufacturer specifies replacing the fuel filter at 30,000 miles, do it. The quality of gasoline may have improved, but filters designed for older vehicles tend to be smaller in size because they were meant to be replaced more often. No matter how you look at things, a smaller filter is going to reach the end of its functional lifespan sooner.
If your filter already has a few miles on it and you’ve accidently run out of gas, we strongly recommend replacing your fuel filter(s) right away - assuming it can be serviced. This is because any aforementioned debris collecting at the bottom of the tank has now been drawn into the fuel pump and sent forward to the filters where it has jammed up. This has an extremely negative effect on fuel flow, and the extra strain of pumping fuel past gunk blockage can often finish off older fuel pumps which would otherwise have some life left in them.
The same logic applies if the vehicle has been regularly driven for a period of time with the fuel level low. What we’re referring to is the person who always drives around on an empty tank, putting no more than $10 of gas in at a shot. When the vehicle draws from the bottom of the tank all the time, fuel filters can become quite clogged. For obvious reasons, this type of driver often suffers from a failed fuel pump.
Modern engines equipped with high-pressure fuel systems have injectors with extremely tight tolerances. Small debris that wouldn’t clog an old fuel injector can permanently damage a new one if fuel passages become blocked. Or, fuel may just drip out of the injectors instead of producing a fine mist spray needed for optimum combustion.
Other Opportune Times To Replace A Fuel Filter
If you’re doing any repairs on the fuel system that require it to be depressurized, then you’ve already done much of the work involved with replacing a serviceable fuel filter.
Naturally, it goes without saying that if you’re replacing your fuel pump, replacing the fuel tank, or dropping the tank out of the vehicle for any reason, there’s no better time to install a new filter. If the filter is built in to the pump assembly on your vehicle, then a new fuel pump will include one.
Work that involves depressurizing the fuel system can include, but not be limited to, working on the injectors, pressure relief valves, cold start valves, carburetor, or even components of the evaporative emissions system. Additionally, accessing or replacing a fuel rail is an opportune time to replace a filter as well. Engine work requiring more involved tear-down (such as cylinder head gasket replacement) may be another excellent opportunity for worry-free replacement of your fuel filter – just be certain the fuel system is fully depressurized first.
When you think about the important role fuel filters play, there’s no reason to let a dirty one dampen your vehicle’s performance, hurt fuel economy, and cost you more money in the way of related repairs.
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