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Fuel in the oil

in 912 / 914 Technical Questions 12 years ago
Gday all my 912 has been running rough l synchronized the carbys found some of my spark plug lead were shorting out l ran the engine to test it again and found oil coming out of the over flow pipe on my oil tank on opening the cap the tank was full petrol must have been getting to the engine.
where can it be coming from please help..
cheers Geoff..

  • Re: Fuel in the oil

    by » 12 years ago

    Hi Geoff, Although not too well versed in the Rotax 912, I have 30 years experience in engines (autos) and, at the risk of sounding an alarmist, I know of only two ways where fuel has found its way into the engine oil. The least serious is via the rear of the fuel pump as it is actuated by a cam from the internals of the engine and hence in an oil environment. Perhaps the diaphragm is punctured and although it should leak out externally, has on occasion worked its way into the engine crankcase.
    The other way is passed the pistons via either a hole in the piston or severe wear at the rings and not necessarily showing as a misfire. This though can be verified either way by a basic compression test or a leak-down test. Also of course by your fuel consumption.
    I do stress though that I am fairly new to the 912 and accept that such little knowledge of the type may be pointing you in the wrong direction.
    Richard
      
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  • Re: Fuel in the oil

    by » 12 years ago

    Hi Richard the engine has done 351hrs l did a compression test a coulple of days before l found the oil and just a standard compression test showed number one was 140 psi two 157 three 150 four 155.
    l will start by testing the fuel pump.
    cheers Geoff..
      
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  • Re: Fuel in the oil

    by » 12 years ago

    Hi Geoff,

    You did a static compression test. Do a leak down test with a test pressure of 80-87 psi normally you will only see a 2-3 psi differential.

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

      
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  • Re: Fuel in the oil

    by » 12 years ago

    Hi all , fuel can get in the oil by the means of bad fuel , it doesn't burn properly and go's past the rings ,new engine or not , and more so with turbo engine. I hope this helps u , I found out the had way ,costed me a new machine !!!
      
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  • Re: Fuel in the oil

    by » 12 years ago

    Hi Geoff

    We recently removed a fuel pump from a CT 912s when removing the engine to replace the sprag clutch and fuel was pouring out of the pump and into the gearbox.

    This has happened several times with people saying that their oil level is rising.

    It will reck your engine and I would suggest you don't run it, fit a new fuel pump, change your oil and filter and prime your oil system before you start the engine as shown in the video section here so as to flush out the old oil from the oil galleries and tappets and pushrod tubes.

    http://www.rotax-owner.com/information-reg/expanded-video-instructions-reg/33-exp-si-912-018

    I would allow at least a litre or two of oil to drain before reconnecting the return pipe.

    Good luck

    Mark
      
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