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Thread: Extremely High Fuel Pressure

  1. #1

    Default Extremely High Fuel Pressure

    I just installed the Atomic with Return line. I bought the Master Kit with the Fuel Return kit. November 2019. I got everything installed and for my first startup, I set the fuel pump to "non-PWM with Regulator". When I turn on ignition key, the fuel pressure goes to over 100 psi (I have a gauge mounted on the Regulator). After a second the fuel drops to zero (this is without starting the engine). When I started the engine and the Atomic Dash and the mechanical gauge shows the fuel pressure is over 100 psi. The engine stalls after a couple of seconds.

    I though the return line might be blocked, so I removed the return line from the TBI and capped the outlet. Then I switched the fuel pump type to "PWM". I started the engine and it read 139 psi on the Atomic Dash. Is that even possible? Engine started ran a second then stopped. There was a code for A/F.

    Next, I reconnected the fuel return line and switched pump type to "PWM with Regulator". This time I was able to maintain 50 psi, and the engine stayed running.
    I thought there might have just been some trash in the fuel pump (perhaps internal high-pressure bypass - if there is one) which is now cleared. So I switched fuel pump type back to "Non-PWM with Regulator" (as the MSD manual says is the recommended setting for adjusting fuel pressure) but the fuel pressure again went over 100 psi. And I have the Regulator adjustment screw backed all the way out.

    So, I went back to "PWM with Regulator". In that setting I can maintain 50 psi fuel pressure and engine runs. What is going on? Is it possible the fuel pump can be putting out over a 100 psi? The manual says the pump is rated for 70 psi and I should set it to 60 psi (for engines with over 400 HP).

  2. #2


    Problem not fixed. I had it stable at 48 psi with pump setting at "PWM with Regulator". This was just idling. I hadn't driven yet, but went I went out for a test ride I see the fuel pressure on the Atomic Dash back up to 95 psi. This is confirmed by the mechanical gauge on the pressure regulator. I'll call MSD on Monday.

  3. #3
    Join Date
    Sep 2017


    Hi Countrybumkin. Reading the other thread with Frank and his C10, I think you got this one sorted out. Glad things are starting to work out.

  4. #4


    It's all sorted out. I had a restriction (pinched) return line. That was causing fuel pressure to creep up high. It's fixed now, and Atomic is working great. Very impressive system.

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