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Thread: G3X MP Sensor Sticking

  1. #1
    stewartb's Avatar
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    G3X MP Sensor Sticking

    Mine stays at 24.7Ē after gradual power reduction below that. Itíll go lower if I abruptly reduce and add throttle and then it hunts upward to catch up, so Iím pretty sure itís a sensor thing. I was caught by surprise. No reason, I guess. Iíve had round MP instruments fail. I just didnít expect it and have never heard anyone mention a sensor failure with a glass panel.
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  2. #2
    Grant's Avatar
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    The old MP sense line fittings would sometimes coke up and give wierd indications. Maybe worth looking at... Where does the MP pull from?

  3. #3
    stewartb's Avatar
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    The intake port at #3 cylinder. I’ll pull the lines and check for fluid but it isn’t acting like a fluid obstruction. At least it’s not my initial thought. The sensor is mounted vertically in a tee that also feeds MP to the Pmags. I’ll check those lines, too, but again, not expecting to find a problem that causes what I’m seeing. But expectations may be wrong.

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    Quote Originally Posted by stewartb View Post
    The intake port at #3 cylinder. I’ll pull the lines and check for fluid but it isn’t acting like a fluid obstruction. At least it’s not my initial thought. The sensor is mounted vertically in a tee that also feeds MP to the Pmags. I’ll check those lines, too, but again, not expecting to find a problem that causes what I’m seeing. But expectations may be wrong.
    Configuration on my FX-3 is the same except LightSpeed instead of Pmags. I have not heard of any problems with the Kavlico MP sensor but anything can fail. How small is the sensing hole on the sensor? Is it clear?

    Should be possible to connect a temporary tube to the sensor and cycle it with a vacuum pump (simple hand operated would work) while running GDU and GEA 24 on IBBS (if fitted).
    Last edited by frequent_flyer; 07-26-2022 at 09:45 AM.

  5. #5
    Grant's Avatar
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    The fitting at the intake port is where the coking occurs. It's not liquid, more like a hardened tar/oil that builds up in the fitting passage.

  6. #6
    stewartb's Avatar
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    Thanks. I appreciate the tip. I'll pull the fitting and inspect it tonight along with the rest of the MP plumbing.

  7. #7
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    System inspected. No leaks, no obstructions. The coking thing must be with carb engines. Mineís FI and the intake port is as clean as it was when installed. Fortunately Spruce had an MP sensor in stock, a welcome surprise given Garmin glass product lead times these days. With the Kavlico snap-off wire caps I donít even have to mess with crimping 22ga wires in cramped spaces. Unscrew one sensor, screw in the other, plug it in.

    Anyone suffering delays in your projects due to Garmin? If youíre thinking of buying Garmin avionics, order it ahead of time. I know of a project thatís dead in the water waiting for a G3X.

  8. #8
    frequent_flyer's Avatar
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    Quote Originally Posted by stewartb View Post
    Anyone suffering delays in your projects due to Garmin? If youíre thinking of buying Garmin avionics, order it ahead of time. I know of a project thatís dead in the water waiting for a G3X.
    Garmin has been unable to supply the GSU 25C ADAHRS for over a year! Don't know what other G3X Touch LRU are unavailable. Andair can't supply fuel pumps either.

    Did you test the MP sensor with a vaccum pump?

  9. #9
    stewartb's Avatar
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    I’ll test it when I go flying. I’m confident it’ll be fixed.

  10. #10
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    Quote Originally Posted by stewartb View Post
    Iíll test it when I go flying. Iím confident itíll be fixed.
    I was wondering if you had checked the old sensor before you removed it.

  11. #11
    stewartb's Avatar
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    Theyíve changed the sensor. Same plug cap but the housingís different and the orifice inside the sensor is completely different. I must not have had the only one that was bad.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  12. #12
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    Due to supply chain issues Garmin sourced a new vendor and created a new version of the engine sensors. Was just announced / released a few weeks ago.


    Sent from my iPhone using SuperCub.Org

  13. #13
    stewartb's Avatar
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    Mine are both Kavlico. I’d read on the RV site that some guys were drilling out the MP sensors. My old one doesn’t have a visible orifice in the stem, the new one does. $89 for new so not the end of the world.

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