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Thread: Fuel System OverPressure 912IS

  1. #21

    Join Date
    Sep 2016
    Location
    Austin, TX
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    42

    Default Re: Fuel System OverPressure 912IS

    Quote Originally Posted by rosslr View Post
    HI Paul

    But I would post again on the Rotax Owners site under the 912is engine thread as there are some pretty wise Rotax heads on that site.

    The second issue about getting the fuel system to seal is worrying. Are you using the copper crush washers that were supplied? I think from memory they might be different sizes at each end of the filter but being away from home I cant verify that.

    Thanks for posting as I find that sharing our thoughts helps create some knowledge around this relatively new engine. Of course, John Mc is pretty experienced with this engine and the fuel manifold setup so it could be worth an email direct to him to ask his views too.
    Good advice, I will reach out to John and post on the Rotax Owners site.

    I tried the particular filter with and without the washers with the same result. There were no washers used when the system was built, so I did not plan to use them. When I replaced the filter it sealed up fine without a washer. Guess it was just a bad one.

  2. #22

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    Sep 2016
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    Austin, TX
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    Default Re: Fuel System OverPressure 912IS

    I owned my Cirrus SR22 for 7 years and don't recall ever talking about the fuel filter. It had fuel injection with 6 cylinders and a lot of fuel flow. I never had an issue. The size of the filter was closer to the one prior to the pump in the Kitfox.

    Just wondering if the cure is worse than the disease here? Did we know there were issues with fuel filtering in the IS previously?

  3. #23

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    Default Re: Fuel System OverPressure 912IS

    Or is it possible that the warning levels are set too low on the Dynon for fuel pressure?

  4. #24

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    Sep 2016
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    Austin, TX
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    Default Re: Fuel System OverPressure 912IS

    For those curious minds, there are new parts to the puzzle.

    Based on feedback from the Rotax Owner forum I adjusted my warning levels on the Dynon to a higher setting. The Red alarm is now at 50psi vs. 47. I was hoping that was it. But unfortunately it looks like I have something else going on.

    I took the plane up to check everything and it was all fine for about 20 minutes of pattern work and so I started out to explore locally. With both pumps on the pressure was in the 45 range. A couple minutes after leveling in to cruise with an RPM of 5300 and fuel pressure of 45 I felt a surge in the engine RPM. I looked down and the RPM had yellow lined and the fuel pressure went to 47. The Lane A light came on and the Dynon warning to land came on. I did not see the pressure hit 50, but it might have for a second. There was nothing in the Dynon to say what had caused the warning. I had to continually pull the throttle back to keep from RPM running up. The pressure backed down to 45 with pump 2 on only. This was exactly the same as before I adjusted the settings the previous week.

    This new information had me pull the cowl and take a look at everything. I specifically looked at the throttle linkage. Everything looked OK. As I worked the throttle the action was not smooth at first. The wire seemed to bunch up a bit and then snap to full open. I worked that a few times and did not see it again.

    I am hoping this is a simple, mechanical thing. Of the big 3 / fuel / air / spark, it still seems to be the fuel. But I am not sure what to investigate at this point.

  5. #25
    Senior Member
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    Dec 2012
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    Mt Beauty, Australia
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    1,073

    Default Re: Fuel System OverPressure 912IS

    Paul, what type of throttle cable do you have? From what you describe it sounds like it could be the throttle - I have a mc Farlane type and if the friction on the vernier is not tight it will creep forward and increase revs but not dramatically - it sounds like your kink in the cable could be a problem and need replacing. HOWEVER, that does not necessarily explain the Lane A light coming on. I am not expert but FWIW I would:

    1. eliminate any possibility of a faultly throttle cable by ordering and installing a new one.

    2. check all the spark plug leads are attached properly

    3. Then suspect injectors - my understanding is that Lane A controls half the injectors and spark plugs and Lane B the other half.

    Beyond that, I am clueless.

    good luck

    r
    Ross
    Mt Beauty, Vic
    OZ
    Sold to Richard and Scott Taubman in OZ, 2019. Kitfox SS7,Rotax 912is Sport, Airmaster CSP 75" blades.
    Landcruiser and Cub off road camper (doesn't get any kudos on this forum!)

  6. #26

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    Sep 2016
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    Austin, TX
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    Default Re: Fuel System OverPressure 912IS

    C57C0A6D-0A25-4CC3-9DEB-B1358CD62372.jpg

    My throttle linkage. Hopefully the picture worked. It was not linked, just seemed to bend a little prior to going full throttle.

  7. #27

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    Sep 2016
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    Austin, TX
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    Default Re: Fuel System OverPressure 912IS

    Update. Last weekend I pulled the fuel system apart and checked the filter again. As I had done before I blew in the filter and there seemed to be no restrictions. I lubricated the throttle cable a bit and went up again. Using the pump 2 the pressure never got above 44.5. No alarms. Maybe it is happy again.

    I was curious and cut open the old filter. Here is what is inside.
    Attached Images Attached Images

  8. #28

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    Sep 2016
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    Austin, TX
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    Default Re: Fuel System OverPressure 912IS

    I really thought I had it. Flew for around 3hrs with multiple stop/starts and no issues. Pressures on pump 2 stayed in the 44 range. Last short flight and just leveling in cruise at 1500 AGL the engine started to rev up, fuel pressure went up, Lane A light and “land the plane” warning came on.

    It almost felt like the throttle snapped open quickly, it freaks the system out, then settles down. But the warning lights will stay on until I restart the engine.

    Not sure what is going on.

  9. #29

    Join Date
    Jun 2009
    Location
    N Little Rock Ar
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    128

    Default Re: Fuel System OverPressure 912IS

    I have not done a first engine run yet But , I have a Stock Flight Systems EMU and the first thing in the manual is to hook up a analog fuel pressure gauge and set the offset up

    I have a rotax fuel pressure sender and it is indicating 15 psi and I have not put fuel in yet

    David Kelm
    7SS 912iS

  10. #30
    Senior Member Av8r_Sed's Avatar
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    Feb 2010
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    10C Greenwood, IL
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    671

    Default Re: Fuel System OverPressure 912IS

    Your Rotax sender sounds suspiciously like it's sensing atmospheric pressure rather than "gauge". Not a problem if the electronics adjusts for it.
    -- Paul S
    Model III SN910
    582 IVO Med

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