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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

    Just for a point of reference...
    All of the 912 and 914 variants (A, F, S, UL, ULS), EXCEPT the 912iS variant, use the same Oil Pump Assembly.

    The 914 has a second pump section that is piggybacked on the main pump.
    It scavages oil from (not pumps to) the Turbocharger.
    In all other respects, the engine side of the 914 Oil Pump is of the common design.

    The Oil pump on the 912iS is a modified version of the original.
    It has a different Pressure Regulator design and the pump section has 6 lobes instead of 4.
    It might be that these changes need to be implemented into the earlier engines.
    The Mounting points for the Oil Pressure and Temperature sensors are present but have not been drilled and tapped.
    These two sensors are mounted on the block of the 912iS at the rear of the engine near the starter.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
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  • Re: Severe Jittering Oil Pressure

    by » 8 years ago

    Hi Ken,
    None of my customers and very few others I have talked to have a very big oil pressure fluctuations. Most are minor or traced back to the digital instrument sample rate, wrongs sensor type in the menu selected, bad sender, poor grounds and mot are easily fixed. You rarely hear of someone that bounces from 0-50 psi constantly or that dramatically.

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

    Thank you said by: Ken Ryan
      
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  • Re: Severe Jittering Oil Pressure

    by » 8 years ago

    To address Bill Hertel's original post suggesting to John that he remove, drain and reinstall the oil filter to see if perhaps its acting as an "air shock". It had tried that sometime back with no improvement as a result, so I don't think the filter is doing any "trapped air" dampening. By the way Bill, thank you much for your informative post! Much good info in there.
    Alex
      
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  • Re: Severe Jittering Oil Pressure

    by » 8 years ago

    A few more wild thoughts...

    If there is an air leak in the oil suction line; when that compressed air bubble met the Regulator valve and decompressed, it would play havoc with the valve.
    The Bubble would be returned to the input side of the tank and re-freshened with more air coming from the leak and the cycle repeats.
    If the leak was at a high point in the hose, like near output connector of the oil Tank, Air could be drawn in without any oil ever leaking out when the engine was off.
    More air would just leak in and the oil would just flow back into the tank.
    Check the hoses and fittings near the Oil tank.

    Rotax has apparently seen or heard enough complaints that they produced the Mushroom Valve as a response.
    They also produced a Video on the subject.
    So this isn't exactly a rare event.

    If you have found this or anyone else's posts to be helpful; feel free to check the "Thank You" Button at the bottom of their posts.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
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  • Re: Severe Jittering Oil Pressure

    by » 8 years ago

    Hi All,update,first flight this morning all went well.flew for 30 mins. with oil pressure stable with minor fluctuations, 2nd flight was NOT good with severs fluctuations from 30- 70 psi,needle was very erratic, i have it on video but not sure how to attach to this forum.
      
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