Fuel pressure issue

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Dieselpowerking, Sep 13, 2018.

  1. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    OP: What you are describing is exactly typical with these duralift E-pump setups. While they are rated for 33gph they really dont keep up the way they should.

    Thewespaul is right that the pump will run fine and dandy at 1psi. While it's not optimal, the difference isnt much. What it boils down to is the timing is slightly different between 1psi and 8psi.
    Mel did a test long ago that confirmed per every 6psi of inlet pressure lost the pump changes 1 degree of timing.

    I have the same inlet pressure issue as do many of us since the duralift pump is such a common mod. Mine runs 11psi at idle and 2psi WOT and my pump is maxed out in all the ways I know to max it. I've recently timed it and so even though it's set at 8.5* BTDC(no load 2000rpm), at WOT that 1* difference will make it more like 7.5* due to the inlet pressure loss.
     
  2. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    If you mean wire gauge, 12 is good for the pump, even for the long run back to your FSV.
     
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  3. genscripter

    genscripter Full Access Member

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    I did a test too. I got about 3psi per 1 degree of timing.



    Depending on where the OP has his timing, on the high or low end, he could easily move out of the optimal timing range if he's consistently dipping down to 0-1 psi at WOT.

    While the e-pump isn't nearly as good as the lift pump at higher RPM's, I think something else is going on here than the pump. I have two e-pumps on my van, one for the diesel and one for my biofuel circuit. My diesel e-pump has decent pressure 4+psi at WOT, and about 8-9psi at idle. However, my biofuel circuit can dip down to 0-1psi at WOT under the right conditions. This is because there are more filters/longer lines/FPHE/and other components that make the biofuel circuit longer and more restrictive.

    I think the OP has a fuel line restriction or filter clog. There shouldn't be any reason why a good duralift pump (he might have a dud), couldn't keep it up to 4psi at WOT unless he pinched a metal line, clogged a fuel line, has a stuck FSV, or kink in a rubber hose.

    If I were the OP, i'd change the filter, and run the truck from a diesel can. Cut out the stock system and see if the e-pump is still weak. Also, Wes' suggestion to rewire the pump will help the power too.



    Also, how many cc's is the IP? If he has some monster IP, it might need a better fuel delivery system than a standard e-pump. Maybe an R&D Stage 1 filter setup?
     
  4. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    I am running a 105 gph e pump on the shop truck and I recently found I am loosing pressure at wot. This is with a heavily tuned stock pump. I know the duralifts are highly recommended for these trucks, but it seems a lot of people have fuel delivery issues. I am going to be upgrading to an 044 pump rated for 215 gph.
     
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  5. 79jasper

    79jasper Chickenhawk

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    It seems anyone running anything over stock settings, drops pressure with the duralift.


    Sent from my SAMSUNG-SM-G930A using Tapatalk
     
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  6. Dieselpowerking

    Dieselpowerking Full Access Member

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    L
    So this is normal for these pumps to do this?
     
  7. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Pretty much
     

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