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Suspected fuel delivery problem, related to boost spike and poor driving?

Posted by brandnew161, Mar 30, 2009

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  1. brandnew161

    brandnew161 Proven Member

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    Alright first i want to say that i searched and could find similar topics but nothing specific. I'd like to narrow down my search as this car is a prospective purchase by wednesay this week. Hence I would like to have some idea of the problem.

    Car, 1995 eagle talon tsi AWD. Car was fully rebuilt including paint job and new suspension. My buddy bought it and now passing it off to me.

    Problem:
    At first the car was not drivable at all, car would bog horribly and had no get up and go. We then did a boost leak test and there was a leak at the injector cyl 3. Bought a new O ring kit and replaced all injector seals. No more air leak. Started car up, a little better but not much. We then noticed that the fuel pressure was low, the gauge was reading 20psi at idle. We replaced the fuel filter and then the pressure went up to 30psi on startup but settled at 26-27psi at idle. Took the car for another test drive and surprisingly made an improvement, the car runs okay but you still cant "floor it", when you do attempt to spool up the turbo the boost gauge will fluctuate between 0-5-10.

    Our opinion now is that the fuel pump may be bad. However the fuel pump is new, we didnt pull it out and dont know the brand except that it is a high flow pump and hardwired. Also there are no leaks in the lines. Now get this, a week or two ago my buddy removed the FPR and the car ran fine, no problems until a few days ago. Any relation? When looking at the fuel pressure guage we also noticed that pressure drops immediately as the key comes out of the ignition. What holds the pressure? If i can narrow down the symptoms to be fuel delivery related what parts should i suspect...pump, sending unit..?

    I appreciate any help, this is my first experience working on a tsi and i hope i can fix the problem so that i can buy this baby :)
     

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    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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  2. Colt4G63 also

    Colt4G63 also Proven Member

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    Check and see where your fuel pressure leaks down when you shut off the pump. It shouldn't be dropping to zero immediately. It could be leaking out of your injectors, or past your regulator, or even backflowing through your pump. Fix that, and then see if you have the correct fuel pressure. It's important to have the correct fuel pressure. Very important.
     

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  3. brandnew161

    brandnew161 Proven Member

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    ok thanks for your help, i will check those and other locations. Since I am not holding pressure there must be some sort of vacuum leak since i am not actually leaking gas. i'll try to locate any broken vacuum lines
     

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  4. Colt4G63 also

    Colt4G63 also Proven Member

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    The leak that causes your fuel pressure to drop instantly would be leaking into your intake manifold or into your fuel tank. How do you know you aren't leaking gas. The pressure drops to somewhere right?
     

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  5. Colt4G63 also

    Colt4G63 also Proven Member

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    The check valve in the fuel pump, the fuel pressure regulator, and the injectors!!! Those are what hold the pressure. I already assumed you weren't leaking gas out into the atmosphere, or I would have mentioned that the fuel lines hold the pressure too.


    BTW: How the hell are you going to loose fuel pressure with the key off, via a vacuum leak?
     

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  6. t25fury

    t25fury Proven Member

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    fuel pump o'ring.
     
  7. wannarace

    wannarace Proven Member

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    If your boost gauge is tied into the FPR vaccum line... the vaccum leak would be the easiest place to start. That would cause your FPR to not hold pressure and make your boost gauge read the way it does. With the fuel pressure, if you pull the line, you have to plug the vaccum line and you should be getting about 43 psi (2G). If you are only reading 30psi then you might have a 1G FPR. With the vaccum line put back on, the pressure will drop 3-5psi. Hope this help a little but sounds like you're on the right track.
     

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    1994 Eagle Talon TSi AWD
    13.900 @ 96.000 · 1G DSM
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  8. Colt4G63 also

    Colt4G63 also Proven Member

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    ^^^ Or that as well. I forgot that. This also would leak into the tank, making it undetectable by walking around the car and looking at it.

    You need to perform a proper fuel system test. See where it's leaking fuel pressure.
     

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  9. Colt4G63 also

    Colt4G63 also Proven Member

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    I don't agree with that at all. If you don't have enough vacuum at your FPR vacuum line, you would see an increase of pressure, not a total loss of pressure.
    Besides there isn't supposed to be any vacuum with the key out.
    1) Zero vacuum equals 43 psi.
    2) More vacuum equals less fuel fuel pressure.
    3) Boost pressure equals more pressure on a 1:1 ratio (43psi base pressure + 10psi boost would equal 53psi fuel pressure)
     

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  10. wannarace

    wannarace Proven Member

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    Yeah, you're right...! Sorry bout that. I was trying to figure why the FPR and the boost gauge wouldn't be working. The main thing though is the FPR. He is only reading 30psi. should be 43psi, that is assuming he's got a '95 ECU. If he's reading 30 psi on a 43psi regulator, then he's got one hell of a leak. My bet is on the o-ring. If it was changed out at some point with an aftermarket pump. Thanks for catching that!
     

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  11. brandnew161

    brandnew161 Proven Member

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    ok i got ya, forget i said anything. I have never done maintainance on a fuel pump, only had to replace one. What am i supposed to be looking for when i locate the check valve? I am also going to reinstall the regulator that came with the car when he purchased it (car ran fine with it). Injectors should be fine, after replacing the rings, the things are brand spankin new.
     

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  12. brandnew161

    brandnew161 Proven Member

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    ^ yea its a 95 ecu but i'm not sure on the specifics of the regulator, i will get the details in a bit

    UPDATE: just texted my buddy and i asked him what regulator was on the car. He said he didnt think that there was one on. Sooo...that doesnt make any sense LOL. Theres a gauge so id assume there was a regulator and not just teed. But if the stock regulator was hooked up wouldnt that be the problem? can the stock regulator handle the High flow pump and 42lb (?) injectors?
     

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  13. Colt4G63 also

    Colt4G63 also Proven Member

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    Nobody said anything about a high flow pump?!? There must be a regulator of some kind or you wouldn't have any fuel pressure. What's screwed to the end of your fuel rail?

    If you have rubber fuel lines (not steel braided), you can clamp fuel lines to check where your pressure is going. Do not clamp any lines with the pump running!

    1) Locate your fuel pump test lead. (If you are running DSMlink and neglected to tell us, you can skip this step)

    2) Turn on your fuel pump with the engine off.

    3) Check fuel pressure, it should say 43psi.

    4) Turn pump off. (The pressure may drop now, but not instantly to zero. It should at very least, hang around 20psi for at least several minutes or hours.)

    5) If pressure drops to zero get ready with an appropriate hose clamping tool. (Needle nose vise grips will work, but a proper line clamp tool would be better for your hoses)

    6) Start the pump again, turn it back off, and immediatly clamp the fuel supply line between the filter and the fuel rail. (You may need an assistant to turn off the pump, so you can clamp the line before you loose pressure)

    7) Observe fuel pressure. If it holds, your pump could be leaking back, or your pump o-ring could be leaking where the pump connects to the sending unit. If it still drops instantly, go to step #8

    8) Unclamp the line, and run the pump again. Immediatly after shutting off the pump, clamp the return line coming out of the pressure regulator, at the other end of the fuel rail.

    9) Observe fuel pressure. If it holds pressure now, your pump, your o-ring, and your injectors are fine, but your regulator is not. If it still looses pressure, go to step #10

    10) Unclamp the line, and get a second clamp ready.

    11) Run the pump again. This time you need to clamp both lines instantly after the pump is shut off. If you are still loosing pressure now, one or more of your injectors is not closing properly.

    Hope that helps, that one's a freebie. Next time I'm billing you! LOL
     

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  14. brandnew161

    brandnew161 Proven Member

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    wow^ thanks a lot for that post, extremely helpful. Thats the first procedure i'm going to try once getting the car.

    Oh and there is braided line extending from the tank.. then there must be an adapter in which rubber hose then connects to the braided line so that it can attach to the mini filter. From there it is all rubber hose
     

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    1995 Eagle Talon TSi AWD
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  15. brandnew161

    brandnew161 Proven Member

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    repost
     

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  16. Colt4G63 also

    Colt4G63 also Proven Member

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    I should also mention, if you loose fuel pressure out of the fuel rail with both lines clamped, you should also check your fpr vacuum line for fuel. If it gets past he regulator pintle, and has a ruptured diapragm, fuel could leak through the vacuum hose into the manifold.

    Remember, be very careful to only clamp the hoses AFTER the pump is shut off. You will have to time it just right if the pressure bleeds down that fast, but if you clamp it with the pump running, you could damage your fuel system, or even yourself. And don't try to clamp any braided hoses.
     

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  17. brandnew161

    brandnew161 Proven Member

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    ^ok i'll be sure to check that as well. Wish me luck, taking a loan out tomorrow then come the work gloves
     

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  18. brandnew161

    brandnew161 Proven Member

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    UPDATE: purchased the car today and took it home to work on it. Here are a few things that i've noted

    1)Stock FPR
    2)I pulled the fuel pump and the o-ring is fine
    3)Gas tank has a lot of built up pressure. When i took the cap off to pump gas it released a lot of pressure(tank was nearly empty)
    4)There is a CEL for the purge valve

    Any insight?

    Tomorrow I am going to do the suggested method above (clamping hoses) to further diagnose the problem.
     

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    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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  19. brandnew161

    brandnew161 Proven Member

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    ok went to do the procedure i mentioned earlier and it was a no go. I took o video of the fuel pressure gauge while i cranked the car and bam!...no pressure what so ever. It drove last night. Maybe with me taking the pump out to check the o-ring last night it did the pump in. I "tried" to just connect the leads to 12v and listen for the pressurization but heard nothing. At least on my focus if you turn the key to "on" you can hear the pressure building. On this car I cant because the pump is hardwired. Anyways, when i connected the leads the pump made a low humming noise. I dont know whats next on this list, i guess buy a new fuel pump.

    Any ideas feel free to toss em in!
    Thanks
     

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    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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  20. brandnew161

    brandnew161 Proven Member

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    bench tested the pump by placing it in a bucket of water and attaching +/- to the leads on the connector pins. Pump still made the low humming noise but did not pump and water out of the bucket.I believe i found the problem.

    The guy who i bought the car from said that the guy before him put in a high flow pump. However should there be a name stamped on the pump anywhere because I am not seeing one. I'm probably going to order a walbro 255.

    Here are some pics of the pump, not sure if its a newer aftermarket one or the stock pump with 100k on it.

    0403091313a.jpg
    0403091313.jpg
     

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    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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  21. Colt4G63 also

    Colt4G63 also Proven Member

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    You might want to order a 190, because everyone says you need an AFPR to run a 255.
     

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  22. brandnew161

    brandnew161 Proven Member

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    alright just wanted to post the results to this thread. Heres what i did
    -replaced denso fuel pump with walbro255
    -removed fuel pump hardire
    -fixed purge valve
    -fixed boost leak on turbo (large o ring on bearing housing)

    Car idles and runs great, cant drive it yet ### its not on the road. Fuel pressure is up from 27psi (before fixes) to 50 psi at idle
     

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    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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