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Fuel Pump - Pressure variation

in 912 / 914 Technical Questions 10 years ago

  • Re: Fuel Pump - Pressure variation

    by » 8 years ago

    Roger,

    While researching my problem, you seemed to be the most knowledgeable, so I'm just jumping in here to get your opinion.

    I own a 2011 Piper Sport with the Rotax 912 ULS. All was fine until I had to do the mandatory fuel pump replacement and 5 year rubber kit. Since both were complete, I have flown about 3 hours.

    Problem 1 - on runup without fuel pump on, I got a low pressure warning, down to +/-2 psi. This lasted for several seconds and then went back up to 3.8. After 3rd takeoff in the pattern, on climb out with fuel pump on, I got the same warning. Later on landing number 5 or 6, same thing. Only on runup and climb out. All other times during cruise, fuel pressure stayed between 3.8 & 4.2.

    Problem 2 - rate of fuel burn seems to fluctuate more than I remember it did. 5,500 RPM cruise showed a rate of 6.8 and then later 6.2. Climb out GPH went up to 7.4 and once even hit 7.8. The red surround warning shows after 7.0 I believe. Is this a problem or is this just normal fluctuations due to random outside or configuration conditions? Could this be related to the fuel pressure issue?

    Thanks and looking forward to hearing from you.

    Eric Schnellbacher
      
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  • Re: Fuel Pump - Pressure variation

    by » 8 years ago

    Hi eric,

    This sounds a lot like air in the system or a poor wire connection.

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

      
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  • Re: Fuel Pump - Pressure variation

    by » 8 years ago

    Did you ever resolve your problem #1?
      
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  • Re: Fuel Pump - Pressure variation

    by » 8 years ago

    Yes.....a few days ago. We talked with Morris Smith of Southern Mississippi Light Aircraft and relocated the incoming or suction line to the engine driven fuel pump. It apparently was routed to close over cylinders 1 & 3 and was thought to be heating up the suction line during a slow climb out and changing the fuel from liquid to gas, or somewhere in between. Switching the aux fuel pump on always cleared the problem. The line was rerouted and now it's a constant 3.8 to 4.2, without the aux pump on.
      
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  • Re: Fuel Pump - Pressure variation

    by » 8 years ago

    What plane is your Rotax in?
    I am in an RV12.
      
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