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Severe Jittering Oil Pressure

in 912 / 914 Technical Questions 9 years ago

  • Re: Severe Jittering Oil Pressure

    by » 8 years ago

    Hi Alex,
    Have you verified the fluctuations with a mechanical gauge? Thereby eliminating an indication error?
    I find it hard to believe the pump would be the problem but we are running out of other ideas.
    I am sure Rotax would cover the pump, if that fixes the problem. Have you got a friend with a 912 that you would lend you his pump to try this?
      
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  • Re: Severe Jittering Oil Pressure

    by » 8 years ago

    Hi Rob,

    I have a mechanical gauge permanently installed in the plane. It agrees with the information I am seeing on the Dynon Skyview, although the Skyview dampens the pressure jittering a bit because of its relatively low sample rate. Please send me your email address and I will email you a video clearly showing the problem on both the mechanical gauge and the Skyview. My email address is alex at fpcounsel dot com. If you wish, I can also send you pictures of the hoses, routing, etc.

    As for borrowing a pump, I don't have any friends good enough to loan me their oil pump for 20+ hours waiting for the issue to re-manifest itself. As I mentioned, once I replace the parts (which I have just done), it will take somewhere between 20 and 50 hours for the issue to come back. I do have access to a pump that has been removed from another 912, but I hate to introduce a possible defective pump into the equation. Further, using that pump would require me to put the beat up spring and mangled screw plug back into the picture. Probably not a good way to trouble shoot this.

    Your continuing help is greatly appreciated.

    Thanks,
    Alex
      
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  • Re: Severe Jittering Oil Pressure

    by » 8 years ago

    Rob,

    Here is an update....
    Wayne (Southland Rotax @ F70) and I spent the last day and a half trouble shooting this. Here is what we did and our conclusion:

    1) Reinstalled old regulator parts (ball, spring and screw plug) and verified trouble was still there.
    2) Temporarily replaced oil hose from cooler to pump inlet. Trouble still there.
    3) Temporarily replaced oil hose from tank outlet to cooler. Trouble still there.
    4) Temporarily replaced oil cooler. Trouble still there.
    5) Replaced oil pump with a used one that Wayne had on hand. SUCCESS. Trouble cleared.

    Inspection of my original pump does not show any obvious defects. Perhaps it's a machining problem with the housing or the impellers? There is no way for us to pinpoint it any further. At this point I would like Rotax to replace the entire pump assembly and the o-ring seals under warrantee. Would you like me to work through Brian at CPS, or directly with you?

    Thanks,
    Alex Erdelyi
      
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  • Re: Severe Jittering Oil Pressure

    by » 8 years ago

    Hi Alex,

    It might be worth flying an hour or two to check it out further. Since you live in the CPS region you'll have to go through them.

    Tell Wayne Roger Lee said hello.

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

      
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  • Re: Severe Jittering Oil Pressure

    by » 7 years ago

    Hello Gents,

    I've got symptoms of a failing oil-pressure transducer on my 912UL, but before I spend money on a new sensor, I intend (as strongly suggested elsewhere) to check the actual oil-pressure using a mechanical gauge.
    Because I have a Flydat unit which locks a hard-fault into the unit which requires removal of the unit and sending it away to be reset, I don't want to compromise the the oil-sensor feed by removing it to put a gauge in-line. After studying the oil-pump diagram, there is a blanked port which is used to feed oil-pressure to a constant-speed prop, so I intend to connect the gauge there. Before I remove the plug to fit an adapter (which I need to purchase) for the gauge, does anyone know the thread-size and type please? I'm guessing it might be M10 possibly fine-thread, but doesn't seem to be specified on any drawings I can find.

    I appreciate your help with this and comments or thoughts you may have.

    Thanks,

    Frank.
      
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