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Hi all,

I have a ROTAX 912 ULS with about 400 hours on it, and I have noticed at times the fuel pressure can jump around a bit.  However, yesterday on descent down from about 8000, I received a Fuel Pressure warning on the glass that was over 6PSI.  I thought it might have been ice, but already had the heaters on.  I levelled out and applied power, and it instantly resolved.

Electric pump was off.

Any thoughts would be great.  

Cheers

John

  • Re: High Fuel Pressure Warning

    by » 3 years ago


    Raise your alarm Point.
    Max Fuel Pressure is 0.5bar (7.26psi).

    A descent can raise the rpm's from the windmilling prop with the throttle at full idle.
    The Higher rpm's and low fuel use can peak the pump pressure.
    The max pressure is limited by the diaphragm Spring.
    No amount of blockage can raise the pressure above spring pressure.

    Do you have a Fuel Return line installed?
    It gives the unused fuel someplace to go.

    My thoughts are that you do not have a problem.


    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.


  • Re: High Fuel Pressure Warning

    by » 3 years ago


    Thanks for that!!

    Return line - That is a good question.  I would need to have a look.  I am not sure what I am looking for, but I will do some research


  • Re: High Fuel Pressure Warning

    by » 3 years ago


    John, if you have 2 fuel hoses passing through the firewall then you have a return line unless you have some very non-standard fuel supply system.


  • Re: High Fuel Pressure Warning

    by » 3 years ago


    Hi Kevin,

    I just ducked down to the hangar to take a look and yes, there are 2 lines through the firewall.

    One goes to the Gascolator and then the electric pump.  The other goes straight to a 4 way connector on top of the motor.

    I have looked in all my manuals and I can see no reference to a return line.  In my past LSA it went to the left tank, but I have asked Bristell for further info. 

    I will let you know when I hear back.

     


  • Re: High Fuel Pressure Warning

    by » 3 years ago


    That 4 way connector should have one fuel line from the pumps, one line to each of the carbs, and then that last line is the return line.  That's usually where the fuel-pressure sensor is too.

    See Rotax Heavy Maintenance Manual, Section 73 (Fuel System), Part 2 (Systems Description)


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