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Thread: MFI electric fuel pump no pressure

  1. #1

    MFI electric fuel pump no pressure

    Ok, my engine is back in my 69S, but I’m not getting enough fuel pressure to the injection pump. I’m getting less than 1lb of pressure out of the fuel pump.
    A little background. The car sat for 30 years and the fuel pump was completely froze up. I took the head off and flooded the armature with WD40 and got everything loosened up. Seems to be spinning freely when 12V applied. I put new O rings in and it is not leaking. Fuel flows freely from tank to pump and from pump inlet (bottom nipple) and out supply nipple (middle). I thought perhaps I clocked it wrong when I reassembled it, but I have tested it in all four positions with no improvement.
    This is very frustrating, as this is all that is keeping the car from driving in 30 years, and my first time to ever drive it!
    Any ideas before I give up and buy a new pump, which at $800+ is not an enduring prospect!
    Thanks for any advice or solutions.
    1969 911S
    1969 Datsun 2000...worth less, but more valuable

  2. #2
    Senior Member majordad's Avatar
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    Dec 2012
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    Cork , Ireland
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    451
    There are better and cheaper pumps out there than the Porsche one

  3. #3
    I have read about the pump offered by Zims, but there seems to be some concern about the lack of a return component. Certainly seems like a viable option however. Any other replacements?
    1969 911S
    1969 Datsun 2000...worth less, but more valuable

  4. #4
    Serial old car rescuer Arne's Avatar
    Join Date
    Aug 2011
    Location
    Eugene, OR
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    1,956
    The Zims MFI fuel pump is on my '72 T right now. I bought and installed it when tracking down a fuel delivery problem. It works fine, the return circuit from the MFI fuel console is sufficient. I repaired my original pump, but am in no hurry to put it back.

    I'm sure the Zims pump is probably a readily available unit, if we only knew the application.
    - Arne
    Current - 2018 718 Cayman, Rhodium Silver, PDK

    Sold - 1972 911T coupe, Silver Metallic; 1984 911 Carrera coupe, Chiffon white; 1973 914 2.0, Saturn Yellow; 1984 944, Silver Metallic

  5. #5
    Senior Member
    Join Date
    Oct 2014
    Location
    Wakefield, RI
    Posts
    110
    I recommend a rebuild by Pacific Fuel Injector. They do quality work at reasonable prices, quick turnover.
    I am very happy with their services.
    -Fred

  6. #6
    The check valve in the pump is probably stuck open. Under that crimped on cap is a valve with a rubber needle seat. You might remove the end piece again and see if the valve is stuck. Also, have you inspected and cleaned the fuel filter sock on the feed side of the fuel tank. If the pump doesn't work I'd suggest a rebuild by "Fuel Injection Corp" so as to not have to modify lines, pump mounting and electrical connections.
    Early S Registry member #90
    R Gruppe member #138
    Fort Worth Tx.

  7. #7
    Thanks for all the replies. Ed, the fuel tank sock has been cleaned and flows freely. I do think that the check valve is the culprit. When you look in the top circular port You can see that the valve protrudes down into the port about half way. Should it be in the up or the down position.
    1969 911S
    1969 Datsun 2000...worth less, but more valuable

  8. #8
    Mostly the check valve has to be free to move against spring tension, and when the piston is released should be free to pop back to a closed position. Beyond solvents to clean up the gunk I have not had any luck duplicating the rubber seals used. You may have to remove that crimped on cap to access the piston.
    Early S Registry member #90
    R Gruppe member #138
    Fort Worth Tx.

  9. #9
    Senior Member
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    Oct 2014
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    Wakefield, RI
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    Humble Pie..
    My above post should have said "Fuel Injection Corporation". I have had no experience with the company that I mistakenly referenced. .Name:  Fuel Injector Corp Inc.jpg
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  10. #10
    I was able to move the check valve piston to the down position and check for pressure again, but no improvement. Since the seal on the piston looked a little compromised and the piston was not moving freely I decided to throw in the towel and make a decision. Rebuild or replace with the Zims. The rebuild option would set me back two, or most likely, three weeks but would be correct and require no modifications. The Zims would probably get me on the road in just a few days and although requiring slight modifications, would be no big deal and easily reversible. In the end I decided that the $150.00 difference in cost would probably be made up by the Bosch most likely lasting longer than the unknown quality of the Zims pump. The hardest part of my decision to go with the rebuild is the long wait time and the fact that our weather will be uncomfortable hot by the time I get the pump back. Oh well, at least I can dribble gas down the stacks and listen to it burble fo a couple of seconds at a time!!
    Thanks for all the advice.
    1969 911S
    1969 Datsun 2000...worth less, but more valuable

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