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Thread: Rotax 912 Fuel Pump Overpressure

  1. #1

    Join Date
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    Default Rotax 912 Fuel Pump Overpressure

    Hello,

    I have about 20 hours on one of the new style "Corona" fuel pumps.

    Yesterday while returning home on a cross country the fuel pressure started drifting. 7, down to 4, up to 7, 8 ,9,10,8,7... All very slow. 10,12,11,13,...eventually I saw 20.

    If the pressure went low I have an electric pump inline but nothing I can do about overpressure. The engine didn't miss a beat and the fuel flow meter stayed constant. I tried clearing the engine a few times without much change.

    Of course I'm thinking instrumentation so before ordering anything I'll need to put another pressure meter on a T and run it on the ground to see. If it all holds steady at 7PSI like it has all along I'm not sure what to think.

    Has anyone heard of a similar problem with the new pump? Or old one for that matter. I'll call Lockwood on Monday and ask the same.

    Thanks in advance,

    Mark Napier
    Building a KF IV Classic
    Original Speedster Wings
    HKS 700e - Can you say speed demon?

  2. #2
    Senior Member Dorsal's Avatar
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    Default Re: Rotax 912 Fuel Pump Overpressure

    Had a similar problem and it turned out to be instrumentation, good call to check that first.
    Dorsal ~~^~~
    Series 7 - Tri-Gear
    912 ULS Warp Drive

  3. #3
    Super Moderator Av8r3400's Avatar
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    Default Re: Rotax 912 Fuel Pump Overpressure

    I have also heard of people needing to add a pressure regulator...
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
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  4. #4
    Dave Holl's Avatar
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    Default Re: Rotax 912 Fuel Pump Overpressure

    I would have thought that if the higher fuel pressures were correct you would have had issues with rough running of the engine as the carb float needle valves would have been overpowered and cause the carbs to flood?
    Dave Holl
    Building Kitfox MK7
    Rotax 912ULS

  5. #5
    Senior Member
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    Default Re: Rotax 912 Fuel Pump Overpressure

    What Dave said makes sense. If those pressures were real, I don't think the engine would run smoothly and normal.

  6. #6
    SWeidemann's Avatar
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    Default Re: Rotax 912 Fuel Pump Overpressure

    Isn't a fuel return line kit (over pressured fuel goes back into the header tank) a good solution to over pressure?

    Skot
    Kitfox Vixen 912 ULS
    N24V at C29

  7. #7
    Super Moderator Av8r3400's Avatar
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    Default Re: Rotax 912 Fuel Pump Overpressure

    The fuel return loop uses a small orifice, .015" diameter, to allow for a small amount of fuel to flow keeping vapor lock from happening.

    This will have little effect in keeping pressure regulated.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
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  8. #8
    Senior Member
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    Default Re: Rotax 912 Fuel Pump Overpressure

    Don't have the experience with the 912, but the same type of carb is used on a Jabiru engine, and at 20 PSI, I'm sure you would be flooding the engine. Bings don't want much pressure. (one of my dead stick landings and discussions with the technical advisor at Bing carb taught me this) Jim Chuk

  9. #9

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    Default Re: Rotax 912 Fuel Pump Overpressure

    I have posted pix of a recent modification I made to my Model 4 Speedster under construction using an aftermarket Holley adjustable fuel regulator that should keep fuel pressure to the carbs constant. Purchased the regulator for about $26 from jegs.

    Last two pix show regulator mounted to my firewall.

    Tom Stuart
    Attached Images Attached Images

  10. #10

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    Raleigh, NC
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    Default Re: Rotax 912 Fuel Pump Overpressure

    Tom,
    Which fuel pressure regulator did you go with?

    Brian
    Brian Cass
    KF Model IV Speedster
    Rotax 912UL

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