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I am installing a new 914 and having problems. The engine will only run with the throttle lever at idle and the choke on. If I try to advance the throttle at all it dies. If I try to let the choke off it dies. The plugs are covered in black soot showing that the engine is running rich. The engine was run on a test stand for about 1 hour total multiple times 3-4 months ago. Since installing on the airplane it has acted like this all but one day it ran fine for about 20 minutes. Today we replaced the 3 way solinoid valve and the fuel pressure regulator with no change. I also disassembled the carbs to check for debris and reassembled them. There is oil inside the air tube coming from the turbo going to the airbox. Any ideas?

  • Re: New 914 will only run at idle

    by » 12 months ago


    Ronald,

    "The engine will only run with the throttle lever at idle and the choke on. If I try to advance the throttle at all it dies. If I try to let the choke off it dies"

    This sounds like classic fuel starvation.

    The engine is running on the choke (rich) circuit - any advance of the throttle is leaning the mixture below sustainable combustion.

    I would check that throttle linkage is working correctly.

    There is no fuel blockage.

    The carburettors have been assembled correctly and moving parts are free, have full movement, without restrictive friction

     


  • Re: New 914 will only run at idle

    by » 12 months ago


    My 914 behaves like that. So my starting procedure is, throttle closed, choke on ,when it starts, choke off while quickly advancing throttle simultaneously. If I don’t advance the throttle quickly enough it usually dies. Don’t hesitate when coming off the choke or stay on it very long or you will just soot up the plugs.


  • Re: New 914 will only run at idle

    by » 12 months ago


    I agree is sounds like fuel starvation but really don’t think that is the issue. We have checked for good fuel flow coming out of the fuel pumps before the regulator that’s on top of the air box as well as fuel flow coming out the regulator on top of the airbox. Both are around 1-1.5 gpm. Fuel pressure reads 5-6 psi. We thought it may a to small of return line issue but took that out the equation by just dumping return fuel back into a bucket. We thought it might be not enough fuel flow from the aircraft wing tank so took that out the equation by using the test stand tank we had that it ran just fine with on the tray stand. 

    Sam how long have you had your 914 and how long has it been an issue having to start it like that? Will try a “quick” start. 


  • Re: New 914 will only run at idle

    by » 12 months ago


    A couple of thoughts. 

    I’ve not seen it myself, but I remember reading about an instance where the turbo impeller got stuck from sitting unused and essentially blocked exhaust and intake air flow.  If I remember correctly the symptoms were similar, the engine would not run above idle.  At least that’s easy to check, just remove the muffler and make sure the turbo spins freely.   

    Also, check out this thread regarding air leaking from the float bowls.

    https://www.rotax-owner.com/en/912-914-technical-questions/7798-914-stalls-above-idle?start=5

     


  • Re: New 914 will only run at idle

    by » 12 months ago


    Good ideas to check, the turbine spins freely and the float bowls hadn’t been touched from the factory until yesterday when I checked for debris in the carbs. I used the same type of gasket and properly torqued the bowl nut. 


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