Constant high fuel pressure on fuel pressure rail

Discussion in '2005+ Mustang GT 4.6L Tech' started by Rod_UK, Apr 22, 2019.

  1. Rod_UK

    Rod_UK Junior Member

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    Hi All,

    I'm in the following situation, I just had a bunch of parts fitted to the car, here's a list of it:

    - Roush CAI (PN: 403913)
    - Ford racing throttle body (PN: M-9926-3V)
    - Brenspeed Detroit Rockers for FI
    - Ford racing rocker and lashes
    - 2.57in M90 supercharger pulley
    - Larger idler pulley
    - BBK long tube headers
    - BBK high flow X-Pypes (will have electronic cutout valves just before the cats)
    - Walbro 400LPH fuel pump (PN: TU281HP-2)

    The car was running fine and the tune has been working well for a little while now. Tune has been done by Lito.

    I stopped the car for about 2-3min and shutoff the engine, when I started it again the engine light was on and my aftermarket fuel pressure gauge was reading (100+ psi), the gauge is mounted on the fuel rail.

    I used the SCT to read and clear the codes but they come back.

    Before I even crack the engine the fuel pressure gauge is already reading off the clock.

    The codes I get are the following:
    P0191
    P0600
    P1237
    P2105
    U0300

    Checked the fuel pressure regulator connector and it is fine.

    So, questions are:
    - What could be causing it?
    - What should I check?
    - Is it safe to even start it?

    Thanks in advance.
     
  2. Screamin_dutch

    Screamin_dutch Member

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    I had this problem when I put a stocj replacement bosch fuel pump in my tank. It was grounded where it shouldnt be, making the pump run on full power as soon as you turned the key. If you hear your pump running all the time, it might be in the wiring.
     
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  3. 06monera96

    06monera96 LeShawno

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    12
    ohh bro! I got the solutions for you cause it cost me 3 hours to figure out this bullshit Walbro did.

    Pull your pump out.

    Look at the ground wire from the pump to the hat.
    I Bet you the idiots grounded it to the body of the pump where that spring is!
    Chop that off and you are good to go!
     
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  4. 06monera96

    06monera96 LeShawno

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    I am surprised lito did not see the issue beforehand. that full ground would send the pump on full tilts.
    I saw 120PSI at the rails, where my Metco gauge pegged out.
     
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  5. 06monera96

    06monera96 LeShawno

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    Here your problem (y) good luck

    upload_2019-4-22_20-12-40.png
     
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  6. Rod_UK

    Rod_UK Junior Member

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    Thanks guys! Lito got back to me with the same solution! Will tackle it when I get the chance.

    Much appreciated your help =D
     
  7. Screamin_dutch

    Screamin_dutch Member

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    Yep same ground on my bosch pump. Drove me nuts troubleshooting. Even ordered another pump and had the same problem again ofcourse.
     
  8. DiMora

    DiMora More Is Better

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    For other users who don't have this problem due to a bad pump, if your FRPS (Fuel Rail Pressure Sensor) goes bad you'll have the same issue. Normal pressure is 39 PSI when everything is running fine on these Mustangs with a returnless style OEM type system; when mine blew up it was hitting 70+ PSI.
     
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  9. Rod_UK

    Rod_UK Junior Member

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    Just an update, got it sorted!

    It was as mentioned, there was a ground wire to be removed, once that was done it ran fine =D
     
  10. Screamin_dutch

    Screamin_dutch Member

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    Good man! Still boggles the mind that all these pumps are sold with wrong wiring
     
    06monera96 likes this.
  11. 06monera96

    06monera96 LeShawno

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    Yup, Walbro told me to kick rocks 6 week to return test send me a new one (skipped this option)
    I took it apart and looked at what was wrong
    poor mechanic was puzzled until we figure out the wiring was wrongly done
     
  12. Laga

    Laga Junior Member

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    I’m pulling up a old thread because I just ordered this pump because it was recommended by Lito. I see the fix above. But once that wire is cut, does it have to be reattached somewhere else? I haven’t even received the pump yet, so I might not have this problem.
     
  13. Rod_UK

    Rod_UK Junior Member

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    No need to connect to anything else, just cut it off
     
  14. Laga

    Laga Junior Member

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    Thanks. Much appreciated.
     
  15. 06monera96

    06monera96 LeShawno

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    been running my walbro for 3 years, she seeing 87% duty cycle but she still delivering fuel (470hp on race fuel) 438 on daily tune)