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Thread: Possible air in return fuel line.

  1. #1
    Senior Member Jack's Avatar
    Join Date:  May 2011

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    Possible air in return fuel line.

    Just replaced all my fuel lines.
    Testing for leaks none found yet.
    Heard strange noise near return line.
    Sounds like a sink running.
    Unplugged frequency valve.
    Unplugged idle motor.
    Unplugged cold start injector.
    Only noise left is fuel pump and the return line noise.
    Haven't fully cranked or started the car yet so it may go away once I run it awhile.
    I don't hear the noise on the feed line.
    I wouldn't think the distributor would let air in with letting fuel out.
    Just asking if anyone else has noticed that noise after replacing your fuel lines?




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  2. #2
    Member AZ-D's Avatar
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    Location:  Ahwatukee,AZ

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    Do you have the RPM relay jumped in this senario?
    Without hearing exactly what you're talking about. If fuel is not leaking anywhere...I'd imagine it's a mostly non issue.


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    Last edited by AZ-D; 01-03-2021 at 03:58 AM.

  3. #3
    Senior Member Bitsyncmaster's Avatar
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    You will hear some noise from the primary pressure regulator. Not sure if that noise is always there when engine is running but I hear it if the pump is running without the engine.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  4. #4
    Senior Member Jack's Avatar
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    https://youtu.be/nnfnq64tXJo


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  5. #5
    '82 T3 FABombjoy's Avatar
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    The return fuel line is noisy - there are some in-line fittings and a 90 degree bend that add to the noise. Mine is almost as noisy at 44psi primary if I turn on the fuel pump.

    Its more noisy & noticeable when the engine is off and no fuel is being injected. The regulator hits the primary pressure target and returns more fuel than in any other running state.
    Luke S :: 10270 :: 82 Grey 5-Speed :: Single Watercooled T3 .60/.48 :: Borla Exhaust :: MSD Ignition :: MS3X Fully SFI Odd-fire EFI :: DevilsOwn Methanol Injection

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  6. #6
    Senior Member Jack's Avatar
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    Quote Originally Posted by FABombjoy View Post
    The return fuel line is noisy - there are some in-line fittings and a 90 degree bend that add to the noise. Mine is almost as noisy at 44psi primary if I turn on the fuel pump.

    Its more noisy & noticeable when the engine is off and no fuel is being injected. The regulator hits the primary pressure target and returns more fuel than in any other running state.
    Okay thanks, at least it's not unheard of, If you'll pardon the pun..

    I certainly never noticed it with the old lines.
    Even with all other components in I could hear it, was going well that's a new noise.

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