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Thread: Auxilary Fuel Pump?

  1. #1
    Bluebird19kf's Avatar
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    Default Auxilary Fuel Pump?

    I noticed someone on the facebook forum added the facet electric fuel pump as an auxiliary pump. Is this necessary seeing as if the mechanical vacuum pump was to fail it should still run with gravity. Thoughts?

  2. #2
    Senior Member Dave S's Avatar
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    Default Re: Auxilary Fuel Pump?

    To get the best answer, might be useful if you mention what engine and model of Kitfox you are considering - quite a few combinations out there.

    Otherwise, there should be a lot of info in the archives which can be accessed through the search function.
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

  3. #3
    Bluebird19kf's Avatar
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    Default Re: Auxilary Fuel Pump?

    Model III with 582. I tried searching but didn't find anything

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    Default Re: Auxilary Fuel Pump?

    Quote Originally Posted by Bluebird19kf View Post
    Model III with 582. I tried searching but didn't find anything
    Not trying to be critical here, but I just did a search for "facet pump" and got back 33 threads many on this exact topic.

    Greg

  5. #5
    Bluebird19kf's Avatar
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    Default Re: Auxilary Fuel Pump?

    Ok, searched for facet pump and got plenty of reading. Thanks. Is it me or are all the discussions talking about the 912. Not sure what the difference would be vs 582 installation.

  6. #6
    tommg13780's Avatar
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    Default Re: Auxilary Fuel Pump?

    I have experience with a 503 rotax single carb using the similar kitfox style wing tank configuration and pulse pump. The pulse tubing was beyond max length (guessing 15-18") therefore the pump was not functioning. This was a replacement engine for this airplane and the pulse pump had about 24" pulse line. Also the fuel lines from wing tank to carb were all 1/4" ID.

    The engine would start and run fine up to around 5000rpm and maintain that. Full throttle was about 6500rpm and it would run about 30 seconds then begin breaking up and the rpm would reduce to around 4000-5000 with intermittent roughness. The 503 is consuming around 6gpm at 6500rpm so at the 5000rpm maybe 4gpm.

    Given:
    1. 503 Rotax w/ single carb
    2. high wing fuel tank with 1/4" ID fuel line
    3. Non functioning pulse pump
    4. No aux pump in the system

    Conclusion:
    Expect to have less fuel available than required to make full throttle 6500rpm for more than approximately 30 seconds. The 582 will be a little more fuel efficient than the 503 due to the rotary valve configuration but not much.

    Diagnosis:
    We shut down the engine by clamping off the fuel line and found the carb bowl to be empty.

    I realize this answer my be slightly indirect to your question but is based on actual real time evidence. I'd suggest that the $50 facet pump would be a good investment in case the pulse pump fails in flight. I believe the 912's are consuming around 3.5gpm so you may lose the mechanical pump without seeing a problem in performance. I hope this helps.

    Suggestion:
    Do an actual fuel flow test on your configuration which is what I should have done and saved myself a bunch of trouble. Like they say, "your actual mileage may vary".
    Last edited by tommg13780; 10-04-2017 at 10:09 AM.

  7. #7
    Senior Member
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    Default Re: Auxilary Fuel Pump?

    Having the forward facing ram air tubes on your wing tank fuel caps is a good idea for improving your fuel flow while in flight as well. JImChuk

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