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Adding "booster" fuel pump to existing fuel pump

akeeneakeene Member Posts: 2
My 99 Tahoe had a failing in-tank fuel pump. It howled, pressure was failing and it had over 180K on it. As a preventative measure I replaced the in-tank fuel pump. Truck ran great for 8 minutes, then lost pressure and died. Not wanting to pull the fuel tank and replace the fuel pump again at that point, I installed a "booster" pump inline to the existing fuel system by adding a high pressure fuel pump just before the fuel filter. I wired the second pump to a dash switch and prior to attempting to start the truck, I just turn on the power to pump #2. The new in-tank pump does not restrict the flow of fuel through it, and any attempt by the in-tank pump to move fuel simply helps the new external fuel pump pick up fuel and pressurize it. Fuel pressure at the fuel rail is back to factory standards (around 64 psi) and the truck runs like new. Does anyone see a problem with a setup like this until I can once again pull the fuel tank and replace the fuel pump again?


  • kiawahkiawah Member Posts: 3,666
    Is the pump wired to a 'key-switched' circuit, where it is only powered when the key is in the on position? You wouldn't want the possibility of the pump running when you weren't there with the vehicle turned on. Forgetting to turn off the pump if wired hot directly to an always on fused circuit would be a problem.

    Also, I don't know if the 99 Tahoe is wired this way, but many vehicles control the power to the fuel pump via the engine computer and/or some safety wreck/rollover switches. In other words, if the vehicle is in an accident, the switch (or relay) is triggered which turns off the power to the fuel pump which prevents gasoline fires from broken fuel lines/parts. Your work around, would have this exposure.
  • akeeneakeene Member Posts: 2
    Yes, I have it wired to an ignition only circuit so that it comes on with the key and goes off when you turn off the key. I first wired it to the fuel pump activation feed, but the booster pump needs more than just the 2 second pressure startup phase. I also mounted a red led on the dash so that I can see if there is power to the booster pump. When testing the other day, the red led went off and the truck died. Looking underneath at my installation I found that a wire had vibrated loose and the pump lost power.

    I now have everything safely mounted and wire-tied in. I have the fuel pump mounted in its original Volvo anti-vibration cage with the cage bolted directly to the frame. I cannot hear the pump running if I am over 3 feet away outside and not at all inside the truck.

    I do plan on repairing the in-tank pump shortly, now that I know how the module comes apart and can replace just the pump and not the entire module. I just have to wait for the snow to stop falling and things to dry out a bit. I plan on leaving the booster pump installed on the truck but not inline with the stock system once I do have it fixed. It will serve as my "get home" fix if needed.

    I have over 200 miles on the installaiton so far with no apparent problems. I did check to see if the pump supplied sufficient fuel for the 5.7 at WOT since the pump was originally designed for a 4 banger Volvo, albeit with a turbo. WOT worked great, hit 95 in a matter of seconds and still accelterating so I think it can handle my normal driving just fine.

    Thanks for asking.
  • bronco14bronco14 Member Posts: 1
    what kind of fuel pump did you use? how long did it take to completely get it installed?
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