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I bought a flying Van’s RV-12 with Rotax 912ULS. Total time on engine is 70 hours. The engine has the new style fuel pump 893110 S/N 13.4493. The engine monitor is a Dynon D-180. I am getting alarms for both high fuel pressure and high fuel flow. Pressure has been as high as 12psi and fuel flows as high as 13gpm. These conditions are spikes. Normally the fuel pressure is steady ~ 7psi and fuel flow is 4-5gpm in cruise flight. The RV-12 has an electric fuel boost pump that is always on. I have pulled the electric fuel pump fuse on occasion and this seems to reduce total fuel pressure. The pressure increases when throttle is reduced in the landing pattern. Sometimes the pressure may also spike in cruise flight but not very often. High fuel flow only happens once in awhile and only happens during cruise flight.

I’m trying to troubleshoot this problem. Is the fuel pressure regulator built into the mechanical fuel pump? Is it adjustable? Does this sound like a mechanical fuel pump problem? Perhaps the fuel pressure sender is going bad? Is the fuel pump capable of producing 12psi. Lastly, can the carburetors work at 12psi fuel pressure?
  • Re: Fuel pressure/flow problem

    by » 9 years ago


    Hi James,

    It isn't the pump doing this. It is electrical in nature. Could be a loose connection or a poor ground or even the input wires to the D180 too close to a radio wire or other energised wire. There is no way to adjust the pumps pressures.
    Right now my fuel pressure alarm is intermittent. It will spike to 12 psi. Seems to happen at high rpms levels and never at low rpms. I have tried all the normal items. My last ditch effort is to re-load the Dynon software and if that fails install new fuel pressure wires. I have tried everything else I could think of. The fuel pressure doesn't really spike and is 4.7 psi.

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


  • Re: Fuel pressure/flow problem

    by » 9 years ago


    Roger - thank you for reply...

    Do you think it wise for now to just increase upper threshold for green, yellow, and red arcs on the Dynon for fuel pressure gage until I can sort out the problem? It would be nice to calm the alarms if fuel pressure is indeed not varying.

  • Re: Fuel pressure/flow problem

    by » 9 years ago


    This one has been a Gremlin to find.

    I have still been flying. My alarm clears automatically. I have no other engine symptoms or fuel issues like leaking or fuel starvation. I know it isn't a real fuel issue and just a wire connection somewhere. I will say it has been elusive. My next move is to re-load the Dynon software and if that doesn't work install two new wires from the sender to the Dynon instrument.
    This never happens at lower rpms, just up in cruise and especially at full throttle during take-off.

    Whether you decide to continue to fly is your choice.

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


  • Re: Fuel pressure/flow problem

    by » 9 years ago


    Roger

    Is your problem strictly fuel pressure on the Dynon or is fuel flow also erratic?

    Jim Stricker

  • Re: Fuel pressure/flow problem

    by » 9 years ago


    Just fuel pressure and only at the higher rpms. I was out today getting ready for my BFR and used lots of full throttle on T&G's and it must have gone off 10 times. I've been out of town for the last few weeks so I'll get it this week.

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


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