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Thread: Replacing your fuel pulsation damper

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    Replacing your fuel pulsation damper

    (First things first: many dankes and salaams to Llamavan for taking the pictures, for being such a wise site administrator, for looking after my vans when I'm overseas, and for being an all-around good person.)

    Hello everyone,

    A couple of days ago I replaced the fuel pulsation damper (FPD) in my '87 4WD.
    What, you may ask, are the symptoms of a bad FPD? The most obvious (and dangerous) one is a strong smell of raw gasoline in your engine compartment, outside the van, and possibly in your van's people compartment.
    If you suspect a gas leak, pull over and stop and investigate the cause! Gasoline is very volatile, has a low "flash point," and will catch fire in less than a heartbeat! Safety first, last, and always - I cannot emphasize this point strongly enough.

    If this job description seems overly detailed to the point of being patronizing, I apologize in advance. I supervise the maintenance and operation of a merchant ship's engineroom for a living, and am accustomed to giving explicit step-by-step instructions in most aspects of the jobs done by those who work for me.

    Prepare for the maintenance before you start turning wrenches. When you remove your FPD, you will inevitably lose some gas out of the fuel rack (pipe) that supplies the injectors. Your van's exhaust manifold (below the FPD) should be cool to the touch before starting. Make sure the space where you replace your FPD is well-ventilated (preferably outdoors), and you have some method of controlling or containing the fuel that will spill.

    You will need a 22 mm open-end wrench for removing and reinstalling the FPD, and a wrench for disconnecting your battery cable. You need not remove the passenger-side engine cover. There are two types of FPDs for our vans; my '86 and '87 take part number 23270-50011 and my '88 takes P/N 23207-16020. Check with your parts source to see which one fits your van, based on your VIN. The gaskets needed for the FPD are the same for all years; they are P/Ns 23232-41081 for the aluminum gasket on the FPD and 90430-12005 for the copper gasket between the banjo fitting and the fuel rack. You will need one spare of each type of gasket per FPD replaced; they should not be reused. More on gasket location and fitting later.

    To cut down the fuel pressure behind the FPD before removing it, you can try running your engine while removing the 15 amp EFI fuse. This picture shows the location of the fuse, right next to the main fuse box under the dashboard, circled in red:

    FPD 1a comp. EFI fuse removed.jpg

    My engine stopped as soon as the EFI fuse was removed; YMMV.

    Once your van is in position for the work, it's a good idea to block the wheels. Next step - remember, safety first - is to disconnect at least one of the battery cables. Now you can start removing the FPD. This picture shows its location, circled in yellow, below the throttle body and intake manifold:

    FPD 2a comp. FPD before highlighted.jpg

    Note the two clamps on the adjacent vacuum hose that have been moved for ease of access. Having skinny fingers and small hands helps when doing this job.

    Once you loosen it, the FPD should screw right out. This is the aforementioned point where you will lose some fuel. If you have to put a bit of muscle into loosening the FPD, make sure you brace the fuel rack to prevent fracturing it.

    This picture shows the copper gasket (P/N 90430-12005) and banjo fitting above the FPD when it is removed:

    FPD 6a comp. FPD Removed.jpg

    This picture shows my used and new FPDs. Note the absence of the machine screw in the top of the old one:

    FPD 5 comp. Both FPDs.jpg

    Now, with the new FPD turned upside down, place a new aluminum gasket (P/N 23232-41081) on its threaded shaft. Remove the old copper gasket from the banjo fitting, clean the banjo fitting's gasket seating surfaces as best you can, and then place a new copper gasket between it and the fuel rack. Getting the gasket centered on the banjo fitting opening is not critical at this point; when you push the FPD into the bottom of the banjo fitting, the gasket will be centered by the shaft. (Just make sure that the gasket does not fall out during the replacement.) You may have to tug a slight bit on the banjo fitting to get it up into its slot on the bottom of the fuel rack.

    When threading the FPD into the fuel rack, be careful not to cross-thread it, or you'll wind up replacing the entire rack. It should thread in easily, once you get it all oriented properly. Using your handy-dandy 22 mm open-end wrench, tighten it until it's snug - don't make it too tight. This picture shows how the new FPD should look once it is installed and tightened:

    FPD 7 comp. New FPD Installed.jpg

    OK, you're done with the installation. Let it sit for a little while to allow the gas fumes to dissipate, then reconnect the battery. If you removed your EFI fuse, now is the time to reinstall it. It's a good idea, but not absolutely necessary, to use the fuel pump to fill up the fuel rack and check for leaks before starting. To do this, locate the fuel pump check connector near the air filter and throttle body. Short out the two connections in it (safety first - use insulated wire!), then turn your ignition key to the "Run" position. You should hear a relay click and the electric fuel pump start. It will take just a few seconds to fill up the fuel rack. If you spot any leaks, shut down immediately and troubleshoot!

    Turn the ignition key to "Off" and remove the fuel pump check connector jumper. Check your work one more time to make sure everything is back in place. With the "hood" still open, start your engine and check again for any fuel leaks; increase engine RPM to the normal range and check again.

    If you have no fuel leaks, sit back with a cold one of your choice and enjoy the satisfaction of a job well-done. B^)
    Attached Images Attached Images
    Last edited by Flounder; 12-26-2010 at 12:53 PM. Reason: Better pictures

  2. #2
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    Re: Replacing your fuel pulsation damper

    Thanks for the awesome write-up Flounder! Very impressive documentation. It cannot be stressed enough the importance of safety here. Like Flounder said, anytime you smell raw gasoline it should be investigated immediately. These FPDs are a common leak point on these vans and I know of several vans that have burned due to a leaky FPD. One of these vans was the white one I wrote up HERE in my body work thread.

    The leak started after I sold the van. The new owner noticed the gas smell but kept driving (did not investigate). A week or so after that the van went up in flames (total loss). It was parked next to his 95 SC All-Trac Previa and that was also lost . Fortunately his losses were limited to these 2 vehicles, as it could have been much much worse. We will never know the exact cause of the fuel leak, but his Fuel Pressure Regulator (FPR) was less than 1 year old so I suspect the FPD. Had he investigated this ASAP, these vans would most likely still be alive. Tim

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    Re: Replacing your fuel pulsation damper

    Always helpful to visit the site...

    '87 4wd is leaking fuel, only while running. Last night I noticed a strong smell of gasoline, but it was nite time and no visible liquid underneath. This am awoke to strong odor again. Turn over ignition only to see if I could see a leak... thought I might blow up. Have not driven vehicle and plan to tow as needed. There appears to be a leak originating from below the oil filter, perhaps a fuel line? After reading this I plan to replace FPD regardless. I'll report back with the cause of failure.


    Happy Holidays!

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    Re: Replacing your fuel pulsation damper

    There are 2 potential leak points in the area you mention. The most likely is the flex line that goes to the under side of the fuel filter. The other is the rubber hose portion of the fuel return line (smaller diameter rubber hose that goes between engine and frame). The bigger line holds about 40 psi, the smaller one is just a return line, so not much pressure here. Tim

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    Question Re: Replacing your fuel pulsation damper

    My 1987 Van FPD is leaking. As in Flounder's picture of old vs new FPDs, it doesn't have a machine screw as pictured in the new one. Could this be the cause of the leak, and could a new screw solve the problem?

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    Re: Replacing your fuel pulsation damper

    Having a screw vs not having a screw is simply a manufacturing style. Some of them have it some of them don't. If it's not leaking from the banjo fitting, then it's leaking due to a torn diaphragm (inside the damper). When this happens the damper needs to be replaced. There are some cheaper options out there, here's a thread where this was recently discussed. Tim

    http://www.toyotavantech.com/forum/s...4117#post14117

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    Re: Replacing your fuel pulsation damper

    Also, FWIW, in the 4Runner FSM to release the fuel pressure you unplug the fuel pump (electrical connector) with the motor running.

    (If you just pull the EFI it will shut off right away, and not release the pressure in the line.)

    ((Alternatively, You could also crank with out the MAF to Throttle body boot on since the MAF sends the signal for the fuel pump to run.))

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    Re: Replacing your fuel pulsation damper

    That wouldn't be so easy on a van. Not sure where the fuel pump connector is on a 4-Runner, but it's underneath on our vans (and they can be a PITA to pull apart). On the van we don't have a MAF. The pump is powered by the circuit opening relay. The COR sends power to the fuel pump when one of, or both, of the following things happen. When the ignition switch is held in the "start" position and/or when the AFM (Air Flow Meter) opens enough to engage the pump switch (pump switch is built into the AFM). It's set up this way because the starter doesn't turn the engine fast enough to generate the air flow required to activate the pump switch. If you simply want to release pressure pull the EFI fuse (#19) with the engine running or crank the starter with that fuse removed. Of course if the FPD is leaking, the fuel pressure will automatically relieve itself whenever the ignition is off. Tim

    Note 1: When working on the fuel system you should remove the gas cap as to remove vapor pressure from the tank.

    Note 2: When you pull the EFI fuse, any stored trouble codes will be erased from the ECU, so it's not a bad idea to check for codes before removing.


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    Re: Replacing your fuel pulsation damper

    My mistake! I meant AFM where I mention a MAF (Flapper with resistor ladder, not heated wire type.) The 4Runner is the same style (AFM), but the fuel pump connector is in the passenger side wheel well and disconnecting is in the FSM.

    You are absolutely spot on about the van fuel pressure relief. I was curious and did a bit of sleuthing :

    No mention of a connector anywhere! And I don't think it would be very accessible...


    And I certainly agree that a leaky dampener will relieve it's own pressure!

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    Re: Replacing your fuel pulsation damper

    I used to always call the AFM the MAF even though I knew better. They have the same initials, just rearranged differently . The job they do is similar too, but after I started posting on forums I had to start paying better attention to terminology (too much confusion when incorrect terms are used). I remember a few months ago I spent hrs searching the forum for incorrect terms I used to use (so I could correct them and/or replace with Toyota's terminology). Of course Toyota has to make things harder by renaming multiple parts with their own names IE: a universal joint becomes a "spider assembly", a harmonic balancer becomes a "crankshaft pulley", a transmission kick-down cable becomes a "throttle cable" wtf?, etc, etc, etc (and the list goes on and on). As if that wasn't bad enough they routinely change terms (depending on what part of the manual you use). Then there's different names called out between the service manual and the parts catalogs . Oh well, all I can do is try to minimize the confusion I create. Sorry, guess I got carried away...............Rant complete . Tim

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    Re: Replacing your fuel pulsation damper

    Ha! No worries, I actually enjoy the disambiguation! AFM and MAF while only different in a letter arrangement are quite different in design!

    It's always best not to confuse those who are still learning (which I always am!)


    (FWIW on the FJ80/62s the screw-type fuel pressure dampener is renown for having the screw fall off and yielding poor fuel economy or a poor idle. One should never tighten this screw as this can cause the diaphragm to rupture, but instead when the motor is off use lock-tight to put the screw in at natural neutral (Flush with surface). Some people also use o-rings around the screw, but that may be micro-managing...)

    (Ref: http://forum.ih8mud.com/threads/what...-thing.220869/)

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    Re: Replacing your fuel pulsation damper

    I've never read or heard Toyota's official explanation of why it's there, but as a tech working on similar systems I think I know (but could be wrong). Here's my understanding of what I think it is: Most pumps make pulsations when they operate. There are also pulsations created when the injectors open and close. The damper is like a small pressure reservoir with a diaphragm and a spring to help compensate and smooth out these pulsations. There are 2 different dampers Toyota used during van production. These different dampers also coincide with the change of the Fuel Pressure Regulator (later year vans have higher pressure FPR's & the different damper). Although these dampers are physically interchangeable, I believe the only difference is in internal spring pressures.

    When you think about it, the diaphragm inside would need to vibrate to coincide with the pulsations. Therefore, under the nominal pressure (determined by the FPR) you would want the diaphragm to be in the neutral position. In order to maintain this, the spring pressure would need to be slightly increased or decrease to offset the different pressure. I'm also assuming that the screw (that's only on some models of dampers) is there to adjust spring pressure by changing it's compression (final step in in manufacturing is to test and adjust as required). It might also be a cost cutting measure so they can use the same damper for systems with different pressures. Lets say they have a thousand dampers all ready to ship, but they don't know which one the auto manufacturer will want. When the order comes in, all they have to do is turn the screw a half turn and "presto" they just changed the part numbers to the ones ordered by the auto maker.

    Of course the alternate way would be to produce 2 different dampers each with a different spring inside (and no adjustment screw). I like this way better because there's no chance of the screw wiggling loose or having some amateur mess with it. How important is the damper? In my opinion it has it's place, but it's not very important. I've heard of people removing them and replacing with a standard banjo bolt, and they reported no difference in performance. Of course people who do things like this probably already have engines that run rough (from all the other crap they've tinkered with). I think the FPD's job is more to take stress off other fuel system components (water hammer effect). It also stands to reason that it would sightly help regulate cylinder performance. Lets say the pulsations range from 25 - 35 psi. If one injector cycles while pressure is at 25, but another cycles while at 35, then they are getting different volumes of fuel (engine might tend to shake at idle and/or one cylinder might tend to run leaner than another). I would expect this to be random and inconsequential, but it's possible at a particular RPM the frequency of the pulsation might match the frequency of the injectors. If that magic RPM is maintained for long periods, then it's conceivable the lean cylinder could sustain damage (but not likely).

    Anyhow, that's the job of the FPD (according to timsrv) . Tim

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    Re: Replacing your fuel pulsation damper

    That's my understanding as well, basically it is a hydraulic shock absorber for the system. There are instances all over the different Yota threads on problems with them backing out, and having poor idle issues, poor take-off, or similar gremlins. Many of the FJ80 guys have pretty wild claims of fuel mileage increases from the adjustment as well (E.g. 12mpg ->16+mpg).

    Here's a great article I found that talks about both sides of the equation:
    http://www.motor.com/magazine/pdfs/012004_08.pdf

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    Re: Replacing your fuel pulsation damper

    That was an interesting read.........and a joy to read after muddling my way through those wacky posts over on that other forum. I had previously decided not to comment regarding those guys, but dammit you got me going. So many lofty claims of increased power and fuel mileage by adjusting a factory set screw (even though most admitted they knew absolutely nothing about it)? JB welding the moving screw in place? putting "o" rings under the screw head to minimize movement........absolute insanity. It was like they were daring each other to F-up their rigs. As I moved from page to page I was desperately hoping somebody with a brain would post and save these guys from themselves............wow....... .

    PS: To be fair there were at least 3 or 4 posts that made sense, but they didn't elaborate nearly enough.

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    Re: Replacing your fuel pulsation damper

    It's almost like a game of "Telephone/Grapevine", only where a bit of fact gets carried on and the overall function gets obscured. I think the o-ring thing starts from some dampers had them from the factory and some didn't. I can even understand the rationale of using blue loc-tite on the screw threads to prevent it from backing out again (If it is possible to get a close to factory adjustment after the screw is removed). The JB weld though leaves me speechless...

    I think it is precisely because the folks with a basic understanding didn't elaborate fully that a lot of assumptions and confusion were occurring!

    (I did like that it was used for a quick-and-dirty, all-or-nothing fuel pressure test for basic troubleshooting.)

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