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Engine Warning Light Question

in General Tech Discussion 7 years ago
I'm looking for some help about my engine warning lamp. I went flying this morning. Stayed in the pattern doing touch and go's. I noticed that the engine warning light would come on whenever I pulled the throttle back to idle. The farther I pulled it back, the brighter it got. It has never come on like that before while the engine is running. The engine seemed to run smooth, no noticeable gaps in power.

Back on the ground, when I shut it down, it seemed to stop harder than normal. I started and stopped it several times and it seemed to jump pretty hard on startup and again stop harder than normal. I pulled the plane back in the hangar and pulled the prop thru several compression cycles while the engine was still hot. It was noticeably harder to pull the prop thru than normal.

After that I decided to pull some of the spark plugs and inspect them. The plugs on the left side were very black. The plugs on the right were light tan. I assume that means the left side is running rich? Is the whole problem due to the carbs being out of balance?

With the top plugs out and after the engine cooled for a bit, I pulled the prop thru a few more cycles. It pulled thru smoothly, no binding or unusual noises noticed.

Any ideas? Thanks!
Aaron Whitaker
Kitfox 730WH

  • Re: Engine Warning Light Question

    by » 7 years ago

    If your rpm drops too low and you have instruments and lights on it can come on. Usually this happens to people on the ground. If you give it more rpm does it go away?

    What year is that engine? How many hours? Possibly some engine fretting.
    Idling too low or long taxi's can cause dry sooty black plugs. It wouldn't hurt to check the carb sync.

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

      
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  • Re: Engine Warning Light Question

    by » 7 years ago

    Thanks Roger. We bought the engine in 2008 brand new. It has 448 hours on the Hobbs. We have been very diligent doing the maintenance. We usually can't get the engine to idle below 1800 rpm. I didn't have any lights on and I noticed the problem while flying. The light would come on at low rpm and go off at high rpm.

    Why the soot on the plugs on the left and not the right? That is a carb balance problem right? Also, what was causing the hard start and stop?
      
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  • Re: Engine Warning Light Question

    by » 7 years ago

    Aaron,

    Understand that the "Engine Warning Lamp" is not a "Check Engine" Lamp in the automotive sense.
    It is a simple GENerator Lamp.
    It comes on when the GEN can not keep up with the electrical loads and the Battery is making up for the shortage.
    It has nothing to do with carburetors, spark plugs, compression, etc.
    You have an electrical issue, not a mechanical one.

    When the lamp comes ON, take notice of the power bus voltage, it is likely below 13v with the lamp ON, and above 14v when OFF.
    This could be caused by a poor electrical connection in the wiring.

    The Hard start can be caused by the starter not spinning the engine fast enough due to the electrical shortage.
    The Hard stop? ???
    A Hot engine will normally be tighter on the tolerances and harder to pull.

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

    Thank you said by: Aaron Whitaker
      
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  • Re: Engine Warning Light Question

    by » 7 years ago

    Thanks Bill, I didn't even think to look at the voltage reading. I will have to go check that. I noticed the problem while flying and I didn't have anything extra turned on, so there shouldn't have been a heavy load on the system that the generator couldn't keep up with. When I was tracing the wire from the warning lamp, I grabbed it right at the connector to the regulator. I gave it a little tug doing so, and it came right out. I wonder if that was the problem. I think I will check the battery too. I wonder if it is a little low because it hasn't been getting charged properly. Seems like it is taking longer to start the engine. I was thinking that it was because we haven't been flying as much lately.

    Sounds like I have an unrelated issue with the sooty spark plugs on the left side. Is that a carb balancing issue then?
      
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  • Re: Engine Warning Light Question

    by » 7 years ago

    A loose generator plug would explain the symptoms.

    The sooty plugs are a fuel issue not related to the GEN Lamp.
    You may have had them all along but never noticed until the lamp caused you to look closer at the engine.
    If your Taxi-IN takes more than 2-3 minute the sooty plugs may just be a fact of life.
    The soot will burn off at the next departure.
    If it is possible to land and shut down as soon as you clear the runway, you can get a better picture of what they looked like in flight.

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

    Thank you said by: Aaron Whitaker
      
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