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Thread: 1971 911S MFI Fuel Pressure?

  1. 05-02-2009, 08:48 PM #1
    Gearbox
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    1971 911S MFI Fuel Pressure?

    Having issues that may be related to fuel pressure. Anyone know the correct fuel pressure for this vehicle? The pump seems to be working and fuel is going through the line, but it doesn't make it past the MFI pump to the injectors. Picking up a guage tomorrow and I'm hoping it's the fuel pump rather the MFI. Thanks Allan
    1971 911S with Factory Recaro Sport Seats, 100% original, Bahia Red/Black

    1974 914 2.0 Yellow/Black

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  2. 05-02-2009, 09:54 PM #2
    Flieger
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    I just took mine apart after the original failed. The commutator was worn down to beyond the point of being a rebuildable core.

    My main resources was the "MFI Pump Open Heart Surgery Part II- the electric fuel pump" thread on Pelican.

    I did a search and found lots of great info from Jeff Higgins, Grady Clay, Early S Man, etc.

    Sorry, I cannot remember the specs right now.

    BTW, I ended up buying a recently rebuilt pump from the Pelican classifieds.
    1971 911S, 2.7RS spec MFI engine, suspension mods, lightened
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  3. 05-03-2009, 08:47 AM #3
    edmayo
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    1971 911S MFI Fuel Pressure?

    If you remove the output line from the fuel pump and plug it directly to a fuel pressure gauge you should see about 35psi of pressure from the pump. The volume spec calls for about a liter in one minute or less. Doing this from memory at home but believe these numbers to be pretty close. Do you know the procedure for checking pressure on the return side of the system at the filter housing? If not I can explain that also.
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  4. 05-05-2009, 05:41 AM #4
    304065
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    Are you following Check Measure Adjust? I wouldn't do anything without going through the sequence.

    Working pressure is 1 bar, relief valve opens at 2 bar. All you are doing is keeping the fuel gallery in the MFI pump filled so it's not a big deal as in EFI.
    1966 911 #304065 Irischgruen
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