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Thread: Bypass Fuel Regulator Won't Adjust

  1. #1

    Default Bypass Fuel Regulator Won't Adjust

    My new 12-841 fuel regulator won't adjust. I can bottom the screw out and no change in fuel pressure. Any ideas?

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  2. #2
    Join Date
    Nov 2013
    Chicago IL


    Are you going in & out of the correct ports?
    Fuel from the pump goes into the sides.
    And the bottom of that regulator goes to the return line or bypass line.

    Also, where are you measuring the fuel pressure at?
    Are you using an electronic sensor or a mechanic gauge to measure it?
    And have you tried a different measuring device?
    Last edited by S2H; 08-01-2016 at 08:47 AM.
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  3. #3

    Default Update

    I checked my fuel free flow to the regulator - strong. I checked my fuel free flow after the regulator - very weak. The regulator is connected correctly. I blocked the return port on the regulator with no change in outlet pressure - very weak. Still unable to adjust regulator at all. I replaced the 12-841 regulator with a 12-803 non-bypass regulator. I blocked one of the outlet ports on the 12-803 regulator and checked fuel flow - strong. I started the car turned the pump on and was able to adjust the outlet pressure to 7 psi at the carburetor inlet.

    I believe that the 12-841 regulator is defective. I took it apart and all the parts look good. There were no restrictions (trash) in the regulator. I have yet to test drive it. About to go do that now.

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