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  • Engine Problems

    In my Bearhawk I have an O-540-B4B5 with an engine driven fuel pump and a fuel boost pump. The fuel pressure censer is located just after the engine driven fuel pump. Twice now when the temperature is over 90 deg on take off about the time I become air borne the engine starts backfiring and losing power so I abort the take off. All of fuel lines forward of the fire wall have fire selves on them. I have been flying it for two years now without any engine problems but the temperatures have not been this hot. Yesterday when I did a full RPM check after the aborted takeoff I noticed the fuel pressure drop to near zero. I am running 91 Octane unleaded non-oxygenated fuel in it. I am thinking it is vapor lock or I have a bad engine driven fuel pump.

    Any ideas on what could be causing this problem?
    LAR

    BH656

    LynnR
    BH 656

  • #2
    Lynn, it's good to see you back and sorry to hear that you are having trouble! Are you familiar with the Lycoming engines Yahoo group? If you aren't already a member and don't want to join, let me know and I can post the message on your behalf.

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    • #3
      Hi Lynn,
      Good to hear you've been flying for two years, some of us at the Bearhawk picnic Tuesday were wondering how it's been going for you.

      I think a good starting point would be a flow test, there could be a restriction/blockage in the system that would make vapor locking more likely in the heat.

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      • #4
        Lynn, Go to 100ll and see the difference. The other fuel may have damaged hoses ect. Stinger

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        • #5
          I have designed my aircraft around the fuel I use so damaged hoses is not the problem but 100LL is a high octane so would not vaporize as easily.
          LynnR
          BH 656

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          • #6
            During the full rpm run up did you have the boost pump on? Where is your fuel pressure sensor located; before, after or in between the pumps?
            Scratch Built 4-place Bearhawk. Continental IO-360, 88” C203 McCauley prop.

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            • #7
              I am going to take out the engine driven fuel pump which will make it possible to shorten the fuel considerable and hopefully make the problem go away.
              LynnR
              BH 656

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              • #8
                The boost pump was on. The pressure sensor is located after the engine driven fuel pump and the boost pump is located before the engine driven fuel pump on the firewall where the fuel line comes through the firewall.
                LynnR
                BH 656

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                • #9
                  Blocked filter before the pump.

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