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How to install UMA fuel pressure gauge on 912 ULS

in 912 / 914 Technical Questions 7 years ago
Hi

I just bought the 7 PSI fuel UMA fuel sensor for my yet-to-be-started 912 ULS but I'm not sure how to hook it up. I can see that the sensor has an 1/8" NPT that I can use to attach (I'm thinking) a hard plastic tube to but what is needed to attach the tube to the hex-shaped looking receptacle on the engine?

Thanks

Paul

  • Re: How to install UMA fuel pressure gauge on 912 ULS

    by » 7 years ago

    The Gauge goes in the fuel line after the fuel pump.
    The fuel sensor will need to be threaded into an 1/8" brass "T" fitting.
    The other two ports in the "T" will need two 1/8" pipe to 3/8 Barbed fittings or similar.

    More compact could be a 1/8" 4-Way Brass fitting.
    Fuel in one. Fuel Gauge on one. Fuel out to each carb on the remaining two.

    Do NOT attach the fuel hose to the threads on the gauge without a brass, NOT Plastic, Fitting.
    Do Not Use plastic fuel line. Marine USCG rated fuel hose Type A-1 is an excellent choice with a 2.5-minute fire rating.
    Placing Silicon Fire sleeving over the hose will buy you a few more minutes to get rescued before the big fire takes over.

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

      
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  • Re: How to install UMA fuel pressure gauge on 912 ULS

    by » 7 years ago

    Hi paul,

    As Bill says attach a metal nipple on the fuel distribution block that is clamped on the carb balance tube. Run a real fuel rated hose in fire sleeve back to the firewall and attach the fuel pressure sender there. Use the proper clamps on the hose and the fire sleeve. NO plastic fittings or plastic poly hose.

    A 7 psi could be a little borderline and 7.2 is the max allowable. A 10 psi may have been better. Even though 3.5-5.5 seems to be the norm it can be higher at times. If you have an auxiliary electric pump you may see an additional .5 to 1 psi increase, but it should not be more than that.

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

      
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  • Re: How to install UMA fuel pressure gauge on 912 ULS

    by » 7 years ago

    Thanks Bill and Roger, this helped a lot. I think I know what to do now, and thank you ever so much for keeping me from the plastic hose idea.

    Paul
      
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  • Re: How to install UMA fuel pressure gauge on 912 ULS

    by » 7 years ago

    Make sure that the pressure sender is ABOVE the connection to the fuel line. The fuel in this pipe is static and with time the lighter elements in the fuel will float up and the heavy ones (tar and bitumen) will sink. If the sender is below your connection the tar etc will sink to the sender and eventually plug it up. If the sender is above your connection the the tar will simply sink back into the fuel line and get sent to the carbs.
    I fitted a UMA differential fuel/air pressure gauge and sender on a 914 and made the mistake of fitting the sender under the connection, after 6 months it plugged up and gave false readings. I wasted a lot of time finding out why.

    Mike G
      
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  • Re: How to install UMA fuel pressure gauge on 912 ULS

    by » 7 years ago

    Just some food for thought.

    I also mounted mine up above the carb balance tube on the firewall and sticking upward. It's been there 8-9 years and never an issue. The guys that come to the shop with them mounted low on the firewall and hanging down have had some clogging. Usually takes 1-2 years, but I end up pulling them and seem to be able to flush them out with some carb spray aimed into the orifice. I do that 4-5 times and it usually seems good to go. This is always with 91 oct auto fuel too. never seem to have an issue with 100LL.

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

      
    Report
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