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My 912iS is installed in an Vans RV12iS. The first time I switched the pumps on without engine running I got 42 and 43 psi indicated on the sky view on pump 1 and 2 respectively.

I have now completed several engine run ups, and with the engine running at approx 2000 rpm pump 1 only produces 39- 41 psi, and similar pressures on pump 2, when only 1 pump is switched on and I get a low pressure fuel warning.

With both pumps on together it rises to 41- 42 psi and sustains it ( up to 43 psi) with higher RPM, but pulling back to idle the pressure drops back to 40 psi with a yellow caution indicated on the sky view in the fuel pressure indicating bar, and sometimes  an audible alert to low fuel pressure 

Has anyone else experienced something similar, and is this just a indicator setting issue or an issue

I have not seen any lower pressure than 39 psi on a low rpm setting, or when I do a pump check by switching one pump off.

thanks

  • Re: Fuel pressure fluctuations

    by » 8 months ago


     I would check your fuel tank strainer and prefilter first for any blockage.


  • Re: Fuel pressure fluctuations

    by » 8 months ago


    I believe this is due to the following.

    The ECU controls the fuel pressure to be about 43 psi "more than the airbox pressure" however many systems show absolute pressure not relative. There are good discussions in the past on this search the form for those. The result is that the fuel pressure reading shows low at partial throttle settings....idle and when you power off to land. I believe this is all normal


  • Re: Fuel pressure fluctuations

    by » 8 months ago


    Perhaps the Dynon correction factor for fuel pressure needs to be adjusted. ( if it has such a correction factor. I know nothing about the Dynon system). My 912is (kitfox SS7), CAN buss is routed to an Advanced 5600. I never see a indication of actual fuel rail pressure. What I see is the output of an atmospheric pressure sensor mounted on a fuel manifold at a point just before the final fuel filter. The advanced 5600 has a math formula which uses airbox MAP and atmospheric pressure as parts of the formula and converts that to a representation of fuel pressure. One time I had a changing fuel pressure while flying and got a Lane B alarm for a bad MAP sensor on the B lane. Changed the B MAP sensor and all was fine.


  • Re: Fuel pressure fluctuations

    by » 8 months ago


    Mark,

    I would first check with other Van's builders with 912iS engines and verify that you have installed everything per plan.  After you are positive that the plumbing and proper pressure sensor is installed per plan and per Dynon installation instructions, I would check that sufficient fuel is reaching the fuel pumps.

    Fuel pressure is regulated by the devise at the end of the fuel rail on the pilot side at the fuel return.  The fuel pressure sensor is probably located between the fuel filter and the fuel pumps.  If the filter is obstructed there would be a pressure rise not a decrease.  If Van's locates the sensor after the filter then there would be a decrease.  If that is the case then obviously check the filter.

    If that is normal the next thing you might do is to buy another fuel sensor.  I have had one fail.  I was having intermittent low pressure indications during cruise flight.

    If everything else is normal I would make sure you don't have a partial obstruction between the fuel tanks and the fuel pumps.  

    I have a Dynon Skyview installation and as long as you are using the 912iS installation kit and hardware the system properly reports the fuel pressure.  You don't have to do any further adjustments or calibration.

     


  • Re: Fuel pressure fluctuations

    by » 8 months ago


    Is your battery in good shape. 


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