06 WRX slight hesitation/bucking, no CEL - Page 2
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This is a discussion on 06 WRX slight hesitation/bucking, no CEL within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; How do you figure? Im not sure I understand the logic... Why isnt the pump maintaining proper pressure? It is ...

  1. #16
    "Supreme Subaphile Extraordinairre" ninefourteener's Avatar
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    How do you figure? Im not sure I understand the logic...

    Why isnt the pump maintaining proper pressure? It is obviously "capable" of producing it.... because it consistently hits 50psi under full boost.

    I wonder if installing an aftermarket adjustable fuel pressure regulator.... and manually increasing fuel pressure will work?

    Even if it does..... this is still really frustrating because that doesnt fix whatever is causing the problem in the first place
    2006 Subaru WRX-Thread: http://www.clubwrx.net/forums/engine-modifications/165158-ninfourteeners-progress-thread-pics.html
    1978 Subaru BRAT-Thread: http://www.clubwrx.net/forums/engine...ss-thread.html
    2007 Subaru B9Tribeca Ltd (PSM)........1994 Subaru SVX LSi(SOLD)
    WRX 12 sec drag (vs. late model Camaro SS):http://www.youtube.com/watch?v=lw0vWdD2cjU
    WRX track racing (catching a stg.2 WRX): http://www.youtube.com/watch?v=mELeSD1Mi08
    Co-Founder/retired Admin-www.slcsubaru.com

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  3. #17
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    I think there is a check valve built into the pump. I have heard of them going bad but I don't remember the symptoms.
    Jeff

  4. #18
    Registered User efmd3's Avatar
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    that's a good idea, see if you can borrow an aftermarket regulator. might be hard to get it on without aftermarket fuel rails or an adapter.

    I feel like its blocked because it sounds like the volume flow rate of the pump has decreased. when there is no fuel leaving the loop it can build the pressure and meet demand, but when the injectors open, which would naturally lower the pressure, the pump can't keep up - it can't increase the flow rate to keep the pressure at the correct level.

    I haven't studied these systems, but that sounds fairly logical to me. I'm just trying to bounce ideas off of you to help find the issue!

  5. #19
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    Look up gss255 check valve problem and you'll see many. Is you car hard to start when cold sitting for a while? That's one symptom of a bad check valve. Some people also mentioned a bad pressure regulator but I'm pretty sure the Subaru don't use these anymore.
    Jeff

  6. #20
    "Supreme Subaphile Extraordinairre" ninefourteener's Avatar
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    Ok.... I see your logic.... and that makes sense. With the same logic though.... it could just be a bad walbro that cant keep up with demand..... or it is slowly on its way out the door.

    Daily driving..... it is fine. In fact, the hesitation issue is intermittent....so its really just a nuisance on the highway...... "sometimes"

    I do have a 1300 mile trip coming up in exactly 1 month though.... so im putting an adjustable fpr on order tonight.... just in case.

    I appreciate your help man..... still looking for other suggestions if anyone has them
    2006 Subaru WRX-Thread: http://www.clubwrx.net/forums/showthread.php?t=165158
    1978 Subaru BRAT-Thread: http://www.clubwrx.net/forums/engine...ss-thread.html
    2007 Subaru B9Tribeca Ltd (PSM)........1994 Subaru SVX LSi(SOLD)
    WRX 12 sec drag (vs. late model Camaro SS):http://www.youtube.com/watch?v=lw0vWdD2cjU
    WRX track racing (catching a stg.2 WRX): http://www.youtube.com/watch?v=mELeSD1Mi08
    Co-Founder/retired Admin-www.slcsubaru.com

  7. #21
    Registered User efmd3's Avatar
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    anytime, i remember reading your build thread waaaaaaaaaaaaaaaaaaaaaaay back, so good luck

  8. #22
    "Supreme Subaphile Extraordinairre" ninefourteener's Avatar
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    No.... car starts right up everytime.... absolutely no problems..... even in below zero temps.
    2006 Subaru WRX-Thread: http://www.clubwrx.net/forums/showthread.php?t=165158
    1978 Subaru BRAT-Thread: http://www.clubwrx.net/forums/engine...ss-thread.html
    2007 Subaru B9Tribeca Ltd (PSM)........1994 Subaru SVX LSi(SOLD)
    WRX 12 sec drag (vs. late model Camaro SS):http://www.youtube.com/watch?v=lw0vWdD2cjU
    WRX track racing (catching a stg.2 WRX): http://www.youtube.com/watch?v=mELeSD1Mi08
    Co-Founder/retired Admin-www.slcsubaru.com

  9. #23
    "Supreme Subaphile Extraordinairre" ninefourteener's Avatar
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    Hey..... with the ignition on..... is my car supposed to hold fuel pressure?

    Been reading. It shoots to 40 when the pump primes.... but then drops to zero.

    Is it supposed to do that?
    2006 Subaru WRX-Thread: http://www.clubwrx.net/forums/showthread.php?t=165158
    1978 Subaru BRAT-Thread: http://www.clubwrx.net/forums/engine...ss-thread.html
    2007 Subaru B9Tribeca Ltd (PSM)........1994 Subaru SVX LSi(SOLD)
    WRX 12 sec drag (vs. late model Camaro SS):http://www.youtube.com/watch?v=lw0vWdD2cjU
    WRX track racing (catching a stg.2 WRX): http://www.youtube.com/watch?v=mELeSD1Mi08
    Co-Founder/retired Admin-www.slcsubaru.com

  10. #24
    Registered User efmd3's Avatar
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    It is supposed to hold pressure, at least mine does (did)

  11. #25
    "Supreme Subaphile Extraordinairre" ninefourteener's Avatar
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    Well that is obviously a problem..... and at least a starting point.

    There has to be some sort of valve that holds pressure somewhere...... which I obviously dont have..... or is significantly broken...... because with the engine off.... pressure drops from 40 during priming..... to zero in 1/10 of a second.
    2006 Subaru WRX-Thread: http://www.clubwrx.net/forums/showthread.php?t=165158
    1978 Subaru BRAT-Thread: http://www.clubwrx.net/forums/engine...ss-thread.html
    2007 Subaru B9Tribeca Ltd (PSM)........1994 Subaru SVX LSi(SOLD)
    WRX 12 sec drag (vs. late model Camaro SS):http://www.youtube.com/watch?v=lw0vWdD2cjU
    WRX track racing (catching a stg.2 WRX): http://www.youtube.com/watch?v=mELeSD1Mi08
    Co-Founder/retired Admin-www.slcsubaru.com

  12. #26
    Registered User efmd3's Avatar
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    yep. did you already check that valve the other guy was talking about?

  13. #27
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    Check valve in the bottom of the pump. It's a spring and a ball bearing. Maybe it to some grit in it and stuck open.
    Jeff

  14. #28
    Good news, everyone! xxxxxxxAnub1s's Avatar
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    914er, I'm in South Jordan, if you ever need a cable to datalog just let me know. I have a Tactrix 1.3u you're welcome to borrow.

    As info, I had a similar problem with my bugeye, turned out to be a cracked sparkplug. I think your issue is probably different though, considering it comes and goes.
    Cody
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    Good news, everyone!

  15. #29
    "Supreme Subaphile Extraordinairre" ninefourteener's Avatar
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    Well..... this weekend I pulled out the fuel pump/filter assembly and discovered that it looks like my OEM filter was not seating properly to the top of the assembly. Factory defect? The rubber grommet used is junk.

    I replaced it... installed an aftermarket high flow filter, and more secure hoses/hose clamps.

    Fuel pressure no longer drops off after the pump has cycled. Ok.... one problem fixed.

    But... I'm still not getting as much pressure as I should be.

    I have discovered that during initial startup.... I get 34 psi at idle.... but after about 30 seconds.... it drops 10psi.

    "Something" is causing the pressure to drop about 30 seconds after I start the car. Any ideas?
    2006 Subaru WRX-Thread: http://www.clubwrx.net/forums/showthread.php?t=165158
    1978 Subaru BRAT-Thread: http://www.clubwrx.net/forums/engine...ss-thread.html
    2007 Subaru B9Tribeca Ltd (PSM)........1994 Subaru SVX LSi(SOLD)
    WRX 12 sec drag (vs. late model Camaro SS):http://www.youtube.com/watch?v=lw0vWdD2cjU
    WRX track racing (catching a stg.2 WRX): http://www.youtube.com/watch?v=mELeSD1Mi08
    Co-Founder/retired Admin-www.slcsubaru.com

  16. #30
    Resident meany-rator 06wrx4me's Avatar
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    Bad wire connection to the pump? Did you check continuity and resistance in the wire?
    2014 Ford Fiesta ST

    06 WRX, HAWKEYE # 001 <T-boned and sold>

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