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912 ULS, 100HP, Will Not Start

in General Tech Discussion 10 years ago

  • Re: 912 ULS, 100HP, Will Not Start

    by » 10 years ago

    Almost sounds like thread sealant. I hope no silicone was used in the fuel system as a sealer.

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

      
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  • Re: 912 ULS, 100HP, Will Not Start

    by » 10 years ago

    The spark plugs faces on the right side (cylinders #1 and #3) are white or slightly grey. On the left side (#2 and #4) the spark plugs faces are black. This, I think, indicates the left side is running rich.

    Because of the black left spark plugs, I took the left carburetor out and completely disassembled it, including the choke. Sprayed carburetor cleaner into everything, followed by air. All the jets appear to be free and open. Turned the mixture screw 1 ½ turns counter clockwise (this was the factory original setting). Installed a new gasket from Lockwood. Put it all back together.

    Fired up the engine today (Feb 22nd) with outside air temperature about 40 degrees. Engine starts fairly easily and runs so-so at 2000rpm; but, at about 2200rpm it starts to get very rough; and, by 2300rpm it feels like the engine is ready to shake itself out of the plane.

    Engine gauges on Dynon Skyview read:
    MAP 20.5
    RPM 2020
    Hobbs 1.5
    Main Gal/Hr 2.3
    Oil PSI 65
    Oil F 72
    Fuel PSI 7.3
    Batt Volts 13.2
    Fuel Gal 3
    CHTL F 99
    CHTR F 135
    EGTL F 971
    EGTR F 118

    Will start cleaning on the right carburetor tomorrow.

    Any other suggestions?

    Oh, the gunk. When I scrapped it out of the carbs fuel inlet, I wiped it on a blue paper towel and let it dry. When dry, it is white. And when you touch it, it turns to a real fine powder. Doubt it is pipe thread sealant as I didn't use any on the fuel lines. But, still a mystery what it is and where it came from. Checked fuel flow at gascolator out, carb fuel inlets and fuel sensor; and, fuel seems to be flowing freely and clear with no gunk.
      
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  • Re: 912 ULS, 100HP, Will Not Start

    by » 10 years ago

    make sure the slide is oriented perfectly in the throat. Even if the diaphragm index is in its slot the slide can be "off"

    miss-alignedslide.jpg (You do not have access to download this file.)
      
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  • Re: 912 ULS, 100HP, Will Not Start

    by » 10 years ago

    You know the white powder can be moisture. I have had carbs come in from the south US with white powder in them from dried water. I had one that was totally covered inside the bowl and the bowls had to be tossed. Is there any pitting in the bowls?

    Maybe the plugs that look to be running leaner are too lean.
    Fuel pressure at 7.3 psi may be flooding the carbs or just a single carb. One needle valve may not be holding back that pressure and or the float arm height may be off.

    One EGT is 971F and the other 118F? Is this a typo?

    I would clean both carbs well. Check the float armature height on both and replace the needle valves.

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

      
    Report

  • Re: 912 ULS, 100HP, Will Not Start

    by » 10 years ago

    Engine is running!

    Ran a couple of gallons through the fuel hoses until they ran clear with fuel. Took the left carburetor apart, and, checked everything (using your suggestions). Fuel inlet to the carburetor looked clean, and, took the fuel inlet jet out and it looked good. Then I sprayed carburetor cleaner into the hole where I had just removed the fuel inlet jet - out flew a bunch of white gunk!

    Put the carburetor back together and did a test engine run. Ran like a sewing machine. Performed like I remember from a year ago. And, ran like the Van's factory plane.

    I think the engine was just starving for fuel any time I got above a idle. Roger, I think that is why the EGTs were different on each side. The EGTs are now the same. All engine gauges are in the green except for the fuel pressure which hovers around 6.7. Not sure whether I should worry about this or not.

    Temperature is about 40 degrees here, so I was unable to get the temperature up to 120 degrees with the cowling off. I have now put the cowling on and will do a test taxi. And, try to get the temperature up to the take off range. Engine is now smooth and surges with power when throttle is applied.

    Appreciate everyone's suggestions to help me get through this frustrating experience.

    Chuck
      
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