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  • Re: New fuel pump

    by » 11 years ago


    Hi Micheal,

    What I did for my FK9 is in this sequence:

    1. reservoir
    2. tube
    3. electrical fuel pump
    4. tube
    5. fuel flow sender (if any)
    6. tube
    7. mechanical fuel pump

    Install in a bypass sense ( 2 T connectors in 2. and 4.) a one way fuel valve because there are some electrical fuel pumps that if they fail they will block fuel flow.

    Check the FACET pump!

    BR Jan

    Thank you said by: Michael Frost

  • Re: New fuel pump

    by » 11 years ago


    ..and a check valve in parallel with the electric pump. The pump is connected to the left tank between the fuel filter and the fuel valve.

    Nice aircraft, I have a WT9 (speed) to

  • Re: New fuel pump

    by » 11 years ago


    I have just installed a new fuel pump on my Tecnam Sierra. The previous fuel pump ran perfectly, but I made the change to be in compliance with the 5 year rubber requirement. My old pump provided a very constant pressure, about .28 bar whether at idle, climb, or cruise. I have a pressure gauge that reads pressure off of the fuel rail.

    After installing the new fuel pump, my pressure ranges from .39 bar (idle or taxi), to .30 bar (cruise), to .20-.21 bar (climb). If I turn on the electric booster pump, the pressure increases to 0.30 bar immediately. Although the pressures I am seeing are in range, I am not comfortable with the large fluctuation. It appears to be that the pump does not have adequate capacity to maintain constant pressure at the engine fuel demand increases. I have spoken to Rotax factory representatives at the LSA expo in Sebring, and they told me that they have not had any problems like this if the Rotax fuel rail is used. The Rotax fuel rail returns less fuel than the one that is supplied by Tecnam. If this is true, then the cost of replacing the new pump is much higher in that the new fuel rail is about $400 for all parts. I contacted Tecnam in the US, and they have not experienced this problem after changing a fuel pump.

    After reading the many posts on this subject, it appears that I am not the only one to experience this issue. I reduced the length of the vent line to get it out of the slip stream, and it provided some help, but the problem is still there.

    I am confident that I have done the installation correctly, and that the pressures that I am seeing are real due to the fact that I have a pressure gauge directly attached to the fuel system that was working the moment before the new fuel pump was installed, and that reads the normal pressure of .30 bar when operated to before starting the engine.

    Although my old pump runs perfectly, I would be out of compliance to re-install it. Keeping the new pump puts me in a situation where I experience significant pressure variation in the fuel system which I find disturbing although Rotax says it is normal and acceptable.

    Any suggestions would be appreciated.

  • Re: New fuel pump

    by » 11 years ago


    Doug,

    The Rotax guys at Sebring may be right. If you reduce the amount of fuel going through the return line, the pump pressure will be more consistant throughout the throttle range. I don't remember the size of the restrictor in the Rotax return, but it is somewhere in the heavy maintenance manual. You don't have to replace the entire fuel rail, just install a smaller inline restrictor orifice somewhere in your return line. The return line restrictor size isn't critical unless it is too large. Smaller is better because all the return line does is prevent vapor lock. Once the engine is running, the return line is not even necessary and many planes don't even use one at all. If you want to check this out easily, just pinch the return line shut and run the engine. Pressures should smooth out.

    If this works, don't get rid of the fuel return line, just put in a smaller restrictor to reduce return flow.

    Bill.

    Thank you said by: Douglas Gunn

  • Re: New fuel pump

    by » 11 years ago


    Doug,

    The Rotax restrictor size is 0.35mm.

    Bill.

    Thank you said by: Douglas Gunn

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