Can’t find proper sending unit

Discussion in 'Tech Discussion' started by BenB, Nov 17, 2018.

  1. BenB

    BenB Junior Member

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    Hey all, new to the site. I have been working on a 91 GMC 3500 4x4 3+3 that had a blown 6.2 diesel in it. I bought the truck with 54000km, absolutely no rot at all! I also had a 90 gmc 4x4 suburban with a 350 tbi that the body was falling off of. I have been working to swap the 350 into my truck, and have everything moved over and recently got it fired up. My problem is I want to keep the duel saddle fuel tanks, but I can’t find the proper sending units that will fit with in-tank electric fuel pumps. I installed an external fuel pump just past the tank selector valve, but it seems the engine is starving for fuel when I give it gas. I suspect it just doesn’t have the suction it needs to pull from the tank(s) through the selector valve. Does anyone know of a sending unit with in-tank electric fuel pumps that will fit into the saddle tanks on the diesel squarebodies? If there’s no such thing, my next plan is to move the fuel pump to between the tank and the selector valve, and install a second pump, one for each tank, and run the whole set up off a relay tied to my tank selector switch. I would rather have them in tank, but not sure that’s possible. Any ideas?
     
  2. Charlie

    Charlie Full Access Member

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    :welcome:
     
  3. 4WDKC

    4WDKC Full Access Member

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    Is there a different between tanks of the diesel and gas engines? Have you looked at the gas senders fro the 87 dualies since it had factory efi?
     
  4. BenB

    BenB Junior Member

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    Thanks for the tip, I did look into then but they look too long for the 20 gal side tanks. Looks like they ran a 60 gal or 80 gal tank with the 454.
     
  5. BenB

    BenB Junior Member

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    I see the s10 ran a 20 gal fuel tank. Anyone know if the sending unit from a 92-94 s10 will fit into my side tanks? I’m going to dig further into this one, might be a good possibility.
     
  6. highdesertrange

    highdesertrange Full Access Member

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    same tanks for a 350 and 454 on a 91 K3500, 20 gallons. the pumps are in tank one in each tank. Rock Auto list the same part numbers for both. the tanks for gas have a baffle in them around the fuel pick up I am not sure if the diesel tanks have this baffle. I would put the correct sending units and pumps in and see what happens. highdesertranger
     
  7. BenB

    BenB Junior Member

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    Awesome, thanks for the info! I did see on some other threads the information about the diesel tanks not having baffles. Seems like some people are keeping the original tanks, and installing an external fuel sump, not sure if that would work for me as it seems they are all talking about performance injection systems operating in the 60 psi range when they use these sumps...
     
  8. Turbolover

    Turbolover Junior Member

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    A sump is just a hole that you cut in the bottom of the tank and place a special fitting that seals the tank back up. The fitting has a port to draw fuel from the bottom of the tank.
    When they started putting in tank fuel pumps on diesels the pumps weren’t very reliable and guys would bypass the in tank pumps with a sump or draw straw and it kept the fuel tank sender functioning.
    It has nothing to do with how much pressure your system runs. It only gives you a place to draw fuel.
     

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