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I just completed my maiden flight in my Kitfox with a 912ULS. It is a new recent engine purchased in 2012 with the latest fuel pump installed. I also have the fuel bypass return option installed. The fuel pressure sensor is a Kavlico purchased with the Rotax 912 sensor kit from Dynon. My pressure readout is on my Dynon Skyview screen. The aircraft is of course a high wing with tanks in the wings and gravity flow to the inlet of the engine driven fuel pump. I do NOT have an auxilliary electric fuel pump.

Everything ran fine on the maiden flight, but during WOT climbs the fuel pressure would hover around the low pressure redline (2.2 psi). As soon as I leveled out in cruise it would be in the green at 4.0 to 5.0 psi. At idle to 2000 rpm it climbs to 6.5 to 7.2 psi. Should I be worried or is this range of pressures normal?

Jim
  • Re: Fuel Pressure Low

    by » 11 years ago


    Hi James,

    This is a little strange. My guess at this point is a bad ground connection (some Dynon's have their mounting bracket grounded too, a bad fuel pressure sender or even a poor performing pump. It would be helpful to put a mechanical gauge inline to check and see which one of these it may be.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


  • Re: Fuel Pressure Low

    by » 11 years ago


    Roger, I will do what you suggest, but what is the "Normal" range of pressures I should see from 1800 rpm idle to WOT climbout?

    Jim

  • Re: Fuel Pressure Low

    by » 11 years ago


    Hi James,

    I believe the average fuel pressure with the new pump is 4.5 - 5.5 psi. It can vary slightly with rpm and if you run an auxiliary pump. Some do see pressures up at 6+ psi. That said many senders and gauges are known to be off and I do mean many. That's why if you think you have an issue then it is wise to put a mechanical gauge inline and double check the reading.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


  • Re: Fuel Pressure Low

    by » 10 years ago


    Hi
    I have a savannahvgxl 150hrs and have exactly the same problem.i have just fitted a NEW pierburg pump and have the same problem.i have an electric pump which I switch on with take off and it helps a bit. I have discussed this with many owners even the New Sling and all seem to have the same problem. They tell me to watch the fuel flow meter anf if the flow is constant then not to worry. I must say I am doing this and the flow rate stays constant without any drop.
    I do not think anybody has the solution .I have tried pumps and guages and still the same and many others have the same.

  • Re: Fuel Pressure Low

    by » 10 years ago


    Neil, there is a much more extensive discussion of this subject in the "general Discussions" area. The thread title is "Low Fuel Pressure Alarm".

    I agree nobody seems to have an answer for this. The factory appears to be ignoring it and pretending it is due to some faulty installation, but there are too many of us with the issue for that to be true. I personally believe the new fuel pump is weak and is just marginally able to do the job at WOT.

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