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Fuel venting/dripping out air filter/intakes 912S

in General Tech Discussion 10 years ago

  • Re: Fuel venting/dripping out air filter/intakes 912S

    by » 10 years ago

    Yes pulled the carbs, flipped upside down and float needle held at 12 PSI with no pressure drop. Meanwhile I switched out to a new carb from a 912 80 HP and had the same problem.... Fuel coming out the air filters in flight. HUH. Does not apper to be a problem with the carbs as I have been chasing.

    Another Rotax expert said to make sure and get full RPM, I am only getting 5600 on climbout not 5800 and make sure the enritchiner/choak circuit is not activating during flight so replaced with stronger springs.

    I am beginning to think this is a design problem with the 912S and the air box was added to fix it. At this point I am designing my own air box that WILL solve the problem since it is not a problem with the carbs.
      
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  • Re: Fuel venting/dripping out air filter/intakes 912S

    by » 10 years ago

    Is this only happening in flight? What exactly is going on when you notice it... Power change, specific throttle setting...?
      
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  • Re: Fuel venting/dripping out air filter/intakes 912S

    by » 10 years ago

    I have been having a similar problem with fuel venting out of the air filters in flight. I have ordered the tools to complete the float valve leak test and will post results when I get it completed. In the mean time, any updates/ideas on the problem?

    Tom Sabean
      
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  • Re: Fuel venting/dripping out air filter/intakes 912S

    by » 10 years ago

    Good question Tom,

    I think it is happening in flight only but I have not done enough testing to conclusively verify this. Generally I get the biggest smell of fuel after I have been at full power climb and go to idle for a descent.

    I just designed an air box and tested it and it solves the problem. This seems like a bandaid fix but I am glad to get rid of the fuel smell and buildup/pooling. However my mechanic wants me to repitch my prop to get full RPM 5800 on climbout and test it without the air box with the air filters directly, which I will do but I am sick and tired of the fuel smell and cleaning the fuel residue from my aircraft.
      
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  • Re: Fuel venting/dripping out air filter/intakes 912S

    by » 10 years ago

    I had the same with my 80hp. You need to consider the possibility your carbs are "shaking" too much at idle. I know it kind of sounds ridiculous if it appears the motor is smooth running but excess carb shake makes them flood because the float valve needle can't sit still! My problem was caused by too soft engine mounts and then the carb to intake rubber boot splitting allowing even more shake. It was happening during descent on final and even when taxiing over rough ground. Once it starts to flood it runs rough and floods more! I think the reason the airbox fixes it is because it holds the carbs still!

    Paul
      
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