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Electric fuel pump

in 912 / 914 Technical Questions 12 years ago

  • Re: Electric fuel pump

    by » 11 years ago

    Hi Ivor,

    The Pierberg and AC pumps are no longer available from Rotax. Pierberg pumps might still be made, but I highly doubt the AC is. Are there any floating around out there? I don't know, but haven't seen any. If you use a different pump you need to make sure you use the proper gasket/spacer between the pump and housing or you could cause problems to the pump or lobe in the gearbox. What's wrong with the new pumps out? They seem to be working fine.

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

      
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  • Re: Electric fuel pump

    by » 11 years ago

    Dear Jim and Rodger,

    Thank you for the replies.

    The problem with my aircraft (low wing) is as follows:
    1. At take-off, the electric pump is switched on and during after take-off checks, when the electric pump is switched off, the fuel pressure drops drastically. I then have to switch on the electric pump when the pressure falls below 0.15 bar.

    2. With the electric pump still on and after gaining height, the throttle is pulled back and the electric pump switched off. In this case, the fuel pressure normally drops to about 0.19 bar before recovering to about 0.23 bar.

    3. The initial pump fitted to the aircraft was an AC, and when the problem first occured, the pump was changed to a BCD pump. This was again changed to another BCD with no change in the pressures as detailed above.

    4. The fuel pressure sensor has been changed with no improvement and a fuel return line fitted to the left tank. The aircraft is fitted with a Dynon D100 and D120.

    5. I am now considering fitting a bypass fuel line around the electric pump as recommended by Rotax.The bypass line will have a check valve and will take off between the gascolator and electric pump and join again between the electric and mechanical pumps. If this does not work then I have no idea what to do.

    The manufacturer has no adea what the problem is except to suggest that the electric fuel pump be changed.
      
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  • Re: Electric fuel pump

    by » 11 years ago

    Hi Ivor,

    Have you installed a new pressure sender and made sure the gauge is correct? Senders are notorious for being wrong. It's usually the first thing I look at.

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

      
    Report

  • Re: Electric fuel pump

    by » 11 years ago

    Hi All,

    There is another issue. Electrical fuel pumps can also fail and thereby blocking the fuel flow. So FK-Lightplanes stipulated for my FK9ELA with a ROTAX 912 UL to install a bypass with an anti return valve.

    Greetings Jan
      
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  • Re: Electric fuel pump

    by » 11 years ago

    Dear Jim and Rodger,

    Thank you for the feedback.
    I checked the fuel pressure sender and guage by installing a mechanical fuel guage into the syatem. The readings on the mechanical guage and Dynon EMS 120 were almost identical.
    After this check, the following 2 installation changes were made:
    1. The position of the fuel pressure sensor was lowered to avoid any air bubbles trapped in the fuel line before the sensor. This was recommended by an AP but I am not sure if this will affect the pressure readings.
    2. The old electric fuel pump was removed and a new Facet electric fuel pump fitted (3 - 4.5 PSI) fitted.

    After a test flight the following fuel pressures were noted:
    1. Before take-off with the electric fuel pump on the pressure went up to 0.45 bar.
    2. During take-off when the electric pump is switched off, the fuel pressure drops marginally to about 0.4 or 0.41 bar. The pressure then oscillates between 0.3 and 0.41 bar using only the mechanical pump.

    I am relieved that the huge pressure drop previously experienced when the electric pump was switched off has been cured but am concerned with the high and fluctuating fuel pressure.

    Any advice?

    Regards,
    Ivor
      
    Report
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