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Fuel Pump

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  • Fuel Pump

    Does anyone know if you have to remove the internal fuel pump from the gas tank when you install a low pressure external pump?
    The internal pump produces approx 45 - 47 psi for fuel injection applications, I have Weber Carbs and am installing a low pressure external Facet Fuel pump that produces 4 - 5.5 psi along with a pressure regulator and fuel pressure gauge to monitor the level and wonder if, with the other pump disabled, will the external pump pull fuel through the disabled pump or do I need to remove the high pressure pump from the tank for proper flow?


  • #2
    It is, ultimately, a question of flow.

    If there are internal restrictions in the submerged fuel pump that doesn't allow it to pass more than a specific number of CCs per minute, the low pressure pump will starve if it tries to suck a greater volume through the disabled pump.

    If you keep your engine under the threshold of 200-210 hp that the stock pump can handle, you should be fine. Above this rating, you may run into restrictor limits and the pump should be removed.

    See this link for instructions on how to remove the stock pump. The pictures link is broken, but I can upload them again if you want them.

    /Magnus F.


    • #3
      Hi Magnus,

      My motor's max HP output is probably 145 - 150 with 95 octan fuel, I have an 1700 Crossflow with a dry sump, 244 cam, open headers with a low restriction silencer and dual 40 DCOE carbs.... so I know I wont be exceeding 200 hp with this motor.... also, I think the fuel flow is 32 GPH.



      • #4
        It should work then.

        To test this, hook up the new low pressure fuel pump to the fuel hose in the engine bay, disconnect the submerged pump and turn on ignition in order to measure the flow through the system. If the new pump does its work according spec, you are fine.

        Don't forget the fire extinguisher...

        /Magnus F.