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Thread: Losing power after 15-20 minutes

  1. #1
    Junior Member
    Join Date
    Nov 2004
    Location
    Austin, TX
    Posts
    28

    Losing power after 15-20 minutes

    '72 911 with 2.4 E and MFI, restoration just finished and took her out for the first "long" drive yesterday. Engine has less 500 miles since rebuild.

    Starts and runs great after about 15-20 minutes (oil temp at 180) starts to lose power and slowly drops off until she stalls. Starts right up again but after a few minutes the power loss and stall comes back. If you let her sit for 15-20 minutes she's good for regular running for another 15-20 minutes then rinse and repeat.

    The fuel pump was leaking so the restoration shop replaced it with a MFI pump made by Genuine (#89517ZR).

    Is the pump over heating? Do I need to replace the pump with a genuine Porsche part or the Zim's kit?

    Thanks.

  2. #2
    Another possible consideration is the condition of the fuel tank unless everything is new and fresh. The filter sock inside the tank for the feed might be collecting debris while under suction until the engine eventually quits...sitting for a bit might 'release' some of the debris allowing sufficient fuel to run fine until it clogs again...as you say, a sort of rinse and repeat thing. Something could indeed be getting hot and failing, but if the tank is old and perhaps crusty, you might pull the sending unit and take a look with a flashlight.

  3. #3
    Had a similar problem a couple of times, on different cars, both traced to a blocked or partially blocked silencer...the wadding inside had fallen apart in both cases and was stopping the gas getting out and building back-pressure....not obvious and took a while to spot in both cases.

  4. #4
    Senior Member
    Join Date
    Oct 2010
    Location
    Southern Ca.
    Posts
    1,166
    How's the check valve on the fuel filter console ?

  5. #5
    Junior Member
    Join Date
    Nov 2004
    Location
    Austin, TX
    Posts
    28
    Solved: Ended up being bad gas and the in-tank filter being gelled over due to sitting for so long. Runs perfectly now!!!

  6. #6
    Quote Originally Posted by mac73s View Post
    Another possible consideration is the condition of the fuel tank unless everything is new and fresh. The filter sock inside the tank for the feed might be collecting debris while under suction until the engine eventually quits...sitting for a bit might 'release' some of the debris allowing sufficient fuel to run fine until it clogs again...as you say, a sort of rinse and repeat thing. Something could indeed be getting hot and failing, but if the tank is old and perhaps crusty, you might pull the sending unit and take a look with a flashlight.
    winner winner chicken dinner - glad it worked out!

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