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Biting the bullet: Converting to electric fuel pump

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Cubey, Jan 23, 2020.

  1. Cubey

    Cubey Full timer RVer

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    The injection pump, I'm guessing.

    Considering I had zero problems before switching, it must be something directly related to the Holley conversion, not an IP problem.

    Doesn't the filter head return line connection have a check valve? Perhaps it's weak and is bleeding pressure from the supply. Just a thought.

    The fuel pressure drops when shut off, as if it's going somewhere. Wouldn't it normally hold pressure? Maybe it's how Holley pumps just are. I had no starting problems with the mech pump so it wasn't losing prime.
     
  2. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    I would plug the return port in the filter head if you have it, I do it on all e pump setups since the e pump has a much easier time pushing air out of the system than the stock pump.
     
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  3. Cubey

    Cubey Full timer RVer

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    Will do. I specifically remember replacing that piece of hose when I did the return lines and o-rings a year ago.
     
  4. Selahdoor

    Selahdoor How can I help you, or make you laugh, today? Supporting Member

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    Put a check valve in that line from the transfer pump.
     
  5. Cubey

    Cubey Full timer RVer

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    Yeah, might a good idea. I think the pump has one.... but there is also still a ball valve before the transfer pump, so i can manually cut off the flow.

    But that shouldn't mess with return line pressute.
     
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  6. Selahdoor

    Selahdoor How can I help you, or make you laugh, today? Supporting Member

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    I was just thinking that if there is no check in the pump, you could be returning fuel to the wrong tank.

    Think I'd add the check valve just as extra assurance.
     
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  7. Cubey

    Cubey Full timer RVer

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    I just ordered this. It'll be here around Monday.

    Screenshot_20200226-211931_eBay.jpg

    I probably won't get to install it until next Thursday due to rain Mon-Wed, but I'm hoping to just sit here parked for at least a week more. Gonna hit the road again soon and won't be back here for at least a year, so maybe my mom won't mind another 7-10 days.

    I will straighten the return line from engine to tank at the tee (no more 90° turn) and check the pressure again. Then I can put on the check valve and reconnect it to the transfer pump.

    I will see if I have the materials on hand for disconnecting the filter head return line connection. I have spare injector caps, clamps, and old used hose bits, so maybe I can come up with a bolts shoved in a hose ends with clamps to plug off both connections.
     
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  8. Cubey

    Cubey Full timer RVer

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    Edit: nevermind. I'm a dork. This post was me being totally wrong. :oops:
     
    Last edited: Feb 27, 2020
  9. Selahdoor

    Selahdoor How can I help you, or make you laugh, today? Supporting Member

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    Where is the "view post before it was edited" button?

    :rotflmao
     
  10. Cubey

    Cubey Full timer RVer

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    I got confused for a few minutes. I mistook the steel supply line from the filter to IP as another return because it's teed off with return.

    So um yeah :joker:

    As in, this:
    (pic from my truck because it's easier to see, but RV is the same)

    20200227_131803.jpg
     
  11. Dane Rickford

    Dane Rickford Full Access Member

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    Is it just me, or would teeing off the return into the pressurized supply line be a possible cause of pressure in the return line?
     
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  12. Cubey

    Cubey Full timer RVer

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    You would think. Both my 6.9s are like that though
     
  13. Dane Rickford

    Dane Rickford Full Access Member

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    Huh, ok. My 94’ 7.3 is set up slightly different, but thats probably due to the year and model
     
  14. Booyah45828

    Booyah45828 Full Access Member

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    No, the little bit of fuel that the tee lets pass into the return system is moot. Truthfully, the return system should be sized large enough that there should be 0 psi present.

    That Tee is designed to bleed air present in the supply system directly to the return, without it having to go through the injection pump. Such as air that would be introduced when changing fuel filters.

    Sometime during 7.3 production they changed to a check valve/nipple on the filter head, vs a nipple on the elbow.
     
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  15. Selahdoor

    Selahdoor How can I help you, or make you laugh, today? Supporting Member

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    Yep. And note, there was a check valve.

    I removed that line and plugged the filter head.

    Re-routed the line to tee with the other line that comes off the top of the IP.
     
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