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Thread: How to change the fuel filter in a vehicle with EFI

  1. #1
    Vulture of The Western World Eric's Avatar
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    How to change the fuel filter in a vehicle with EFI

    One of the most important routine service procedures is changing a vehicle's fuel filter. The filter traps bits of debris and other contaminants that got into the fuel (or your vehicle's gas tank), while allowing the fuel itself to flow freely into the injectors upstream. Over time, the filter needs to changed because the filtering media inside the filter gets saturated with debris, which eventually limits its ability to trap more debris and/or restricts fuel flow to the engine.

    The typical changeout interval is every 15,000 miles or once annually (check your owner's manual for the specific interval recommended for your vehicle). Many people either forget to change the filter per the recommendations or pay a shop to do it. But this is a job you can often do yourself, with a few basic hand tools, in about 15 minutes.

    Here's how:

    * Find out where the fuel filter is located on the vehicle. You will probably need a shop manual for that because it's not like in the old days, when cars had carburetors and the fuel filter was usually obvious and spliced right into the fuel line just before it reached the carburetor. Haynes and Chilton both sell good ones that cover most basic service procedures for just about any vehicle; you can buy a manual for around $25 at most any auto parts store.

    (For purposes of this discussion, I will describe replacing the fuel filter on a late model Nissan Frontier pick-up. On this vehicle, the fuel filter is located on the underside of the passenger floorpan, near the frame rail, about halfway between the rear of the vehicle and the engine compartment.)

    * Obtain a good quality replacement filter.

    * Raise and safely support the vehicle sufficiently to give you working room to get at the old filter.

    In the case of the Frontier, the filter is a small metal canister that plugs into the metal fuel lines with two sections of rubber hose (one on each end of the filter), secured with hose clamps.

    * Use a small vise grip or similar locking pliers (or a hemostat) to gently clamp down on each end of rubber hose to staunch fuel flow as you remove the old filter. Do not use too much clamping force or you may damage the rubber hose.

    * Loosen the hose clamps that secure the rubber fuel hoses, then slip the ends of the rubber fuel hoses off the filter. Some fuel will spill out of the filter body but it will not be much. Remove any bolts/brackets securing the filter to the vehicle and remove the filter - being careful to note its orientation, front to rear. The new filter must be installed in the same direction as the old one and there should be an arrow stamped into the body of the filter but it's smart to use the old filter as a guide.

    * Check the physical condition of the rubber hoses; if they appear damaged/deteriorated you should stop and go back to the auto parts store to get new sections in the same diameter. Take a section of the old hose with you as a sample and be sure you get hose designed for fuel injected applications, can handle the higher line pressures found in EFI systems. If you use a hose designed for carbureted applications, it may leak or even burst and lead to a fire. Same with the clamps. Be sure you use replacements designed for EFI and not those el cheapo worm clamp ones used on older cars with carburetors.

    * Work the new filter into place, being sure it is installed in the right direction. Tighten the clamps, secure any mounting bolts/brackets.

    * Release the vise grips/pliers and look for any signs of leaks. If none, lower the car and start the engine - then check again for any signs of leaks. If you find any, check your work and retighten any clamps that were loose or fix any connections you made that weren't right.

    If no leaks, you're done and good for another year or 15,000 miles!

  2. #2
    Senior Member DonTom's Avatar
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    Quote Originally Posted by Eric View Post
    One of the most important routine service procedures is changing a vehicle's fuel filter. The filter traps bits of debris and other contaminants that got into the fuel (or your vehicle's gas tank), while allowing the fuel itself to flow freely into the injectors upstream. Over time, the filter needs to changed because the filtering media inside the filter gets saturated with debris, which eventually limits its ability to trap more debris and/or restricts fuel flow to the engine.

    The typical changeout interval is every 15,000 miles or once annually (check your owner's manual for the specific interval recommended for your vehicle). Many people either forget to change the filter per the recommendations or pay a shop to do it. But this is a job you can often do yourself, with a few basic hand tools, in about 15 minutes.

    Here's how:

    * Find out where the fuel filter is located on the vehicle. You will probably need a shop manual for that because it's not like in the old days, when cars had carburetors and the fuel filter was usually obvious and spliced right into the fuel line just before it reached the carburetor. Haynes and Chilton both sell good ones that cover most basic service procedures for just about any vehicle; you can buy a manual for around $25 at most any auto parts store.

    (For purposes of this discussion, I will describe replacing the fuel filter on a late model Nissan Frontier pick-up. On this vehicle, the fuel filter is located on the underside of the passenger floorpan, near the frame rail, about halfway between the rear of the vehicle and the engine compartment.)

    * Obtain a good quality replacement filter.

    * Raise and safely support the vehicle sufficiently to give you working room to get at the old filter.

    In the case of the Frontier, the filter is a small metal canister that plugs into the metal fuel lines with two sections of rubber hose (one on each end of the filter), secured with hose clamps.

    * Use a small vise grip or similar locking pliers (or a hemostat) to gently clamp down on each end of rubber hose to staunch fuel flow as you remove the old filter. Do not use too much clamping force or you may damage the rubber hose.

    * Loosen the hose clamps that secure the rubber fuel hoses, then slip the ends of the rubber fuel hoses off the filter. Some fuel will spill out of the filter body but it will not be much. Remove any bolts/brackets securing the filter to the vehicle and remove the filter - being careful to note its orientation, front to rear. The new filter must be installed in the same direction as the old one and there should be an arrow stamped into the body of the filter but it's smart to use the old filter as a guide.

    * Check the physical condition of the rubber hoses; if they appear damaged/deteriorated you should stop and go back to the auto parts store to get new sections in the same diameter. Take a section of the old hose with you as a sample and be sure you get hose designed for fuel injected applications, can handle the higher line pressures found in EFI systems. If you use a hose designed for carbureted applications, it may leak or even burst and lead to a fire. Same with the clamps. Be sure you use replacements designed for EFI and not those el cheapo worm clamp ones used on older cars with carburetors.

    * Work the new filter into place, being sure it is installed in the right direction. Tighten the clamps, secure any mounting bolts/brackets.

    * Release the vise grips/pliers and look for any signs of leaks. If none, lower the car and start the engine - then check again for any signs of leaks. If you find any, check your work and retighten any clamps that were loose or fix any connections you made that weren't right.

    If no leaks, you're done and good for another year or 15,000 miles!
    Good thing I am here to keep an eye on you what you post!

    With EFI, the fuel pump is usually in the gas tank. Any fuel after that point can be above 50 PSI or so, even when the engine is off. Since the fuel filter is often after the pump with EFI (so you can get to it!), it's important to release the fuel pressure. One simple way is to use a fuel pressure gauge with a rag while the engine is off. A better way, in vehicles that have a separate fuse for the fuel pump, is to remove that fuse and start the engine and leave it running until it dies. This will make the job safer and much less messy. You most likely will find that the vice grips (to pinch the hoses) are not needed when you do this job the correct way. Not much fuel gets past most turned off fuel pumps.

    -Don- SSF, CA





  3. #3
    Vulture of The Western World Eric's Avatar
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    Quote Originally Posted by DonTom View Post
    Good thing I am here to keep an eye on you what you post!

    With EFI, the fuel pump is usually in the gas tank. Any fuel after that point can be above 50 PSI or so, even when the engine is off. Since the fuel filter is often after the pump with EFI (so you can get to it!), it's important to release the fuel pressure. One simple way is to use a fuel pressure gauge with a rag while the engine is off. A better way, in vehicles that have a separate fuse for the fuel pump, is to remove that fuse and start the engine and leave it running until it dies. This will make the job safer and much less messy. You most likely will find that the vice grips (to pinch the hoses) are not needed when you do this job the correct way. Not much fuel gets past most turned off fuel pumps.

    -Don- SSF, CA





    Good info, Don - though I have never had a problem doing it as described. It may just be that I haven't done this job on a vehicle that maintains high pressure with the ignition off. I realize the system primes itself to high pressure with the ignition on, but when the key is off, isn't it true that there's only residual pressure in the line? In which case, clamping the hose will staunch most of the flow, since the pump isn't actually pushing any more fuel at this point - and won't until you turn the ignition switch to "run" again.

    Ja?

  4. #4
    Senior Member DonTom's Avatar
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    Quote Originally Posted by Eric View Post
    Good info, Don - though I have never had a problem doing it as described. It may just be that I haven't done this job on a vehicle that maintains high pressure with the ignition off. I realize the system primes itself to high pressure with the ignition on, but when the key is off, isn't it true that there's only residual pressure in the line? In which case, clamping the hose will staunch most of the flow, since the pump isn't actually pushing any more fuel at this point - and won't until you turn the ignition switch to "run" again.?
    Some systems hold the pressure for quite some time after ignition is off (perhaps for several days) but some don't, has been my experience. But it's always better to be safe than sorry. AFAIK, every service manual for a MPFI vehicle tells you to release the fuel PSI before working on the fuel line or changing the fuel filter.

    I know my 2000 RV uses 50 PSI of fuel pressure when the ignition is turned on. Stays within a few PSI of 50 PSI at any RPM, even zero (ignition on but engine not running). When the ignition is shut off, it drops less than 5 PSI even after a minute later. But I don't know how much it lowers if I wait an hour (or a day) as I never checked for such in this RV. But I assume it will still have some fuel pressure even significantly later, because I cannot see it drop while watching for several seconds after the ignition has been turned off for a minute or so.

    So that leaves about 45 psi of fuel, at least for a while. I am sure it varies greatly from one vehicle to the next.

    But if you remove the fuel pressure in advance to changing the filter, who cares how long it holds?

    -Don- SF, CA

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