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The title kinda explains it. The engine is a ULS in a -12. Today out of nowhere in a slow climb at WOT  5400 RPM I could feel a slight miss. I did a mag check and with side A off there was a severe miss. I landed at my destination and let it cool down and on the return flight I did more testing and the severity of the miss with A off reduced as I reduced RPM, at 5000 RPM the miss was gone. The type of miss was more random like not every revolution. 
After landing I did mag checks from 3000 to WOT 5100 RPM and there was no miss. 
I have not had a chance to pull the cowl and look for obvious issues, loose plug wire, etc. 

I’m throwing this out here to create a list of things to look for, easiest / cheapest to ….  Since re-cowling and flying is the only way to test the work. 


Walt

my blog; waltsrv12.com

  • Re: miss side A only above 5000 RPM

    by » one month ago


    Start by checking the simplest/cheapest - spark plug caps/leads & the plugs themselves. 

    Look for loose cap, plug fouling/damaged electrodes. Move on to lead damage, continuity/resistance.


  • Re: miss side A only above 5000 RPM

    by » one month ago


    Hi Walt

    On a ULS you can do a quick troubleshooting by removing the connector plug from the A module and switch it to the B.  If the problem moves with the connector then you are not chasing a problem with the module. 

    Cheers

    40113_2_SMD modules.jpg (You do not have access to download this file.)

  • Re: miss side A only above 5000 RPM

    by » one month ago


    Sean, that is what I was thinking. The wires and caps are new within 50 hours. Of course that doesn’t mean anything. I have a hunch it’s a plug that is fouling at the high rpm/load. I was trying to think of a matrix to narrow down if it is spark plug related without changing all. My thought is to swap the plugs front to back on the tops and bottoms. If the miss changes mags then it is a plug issue. 


    Walt

    my blog; waltsrv12.com


  • Re: miss side A only above 5000 RPM

    by » one month ago


    "The wires and caps are new within 50 hours. "

    Double check your workmanship. A bad connection in the HT system can result in a spark jump at lower rpm, that fails at higher ,causing a miss.


  • Re: miss side A only above 5000 RPM

    by » one month ago


    today I swapped the top plugs front to back, an easy test without removing the lower cowl. If one of the plugs was a problem the miss should have moved to the B ignition. The test flight both sides worked perfectly for the first 5 minutes then the same A started missing. So not the top plugs. 
    Off with the bottom down and get more serious. I pulled the bottom plugs, they looked good. In the process looking at the wires, see pic. Every plug wire was, melted where it goes into the cap. These wires are questionable. I bought bulk 7mm wire from Spruce when I replaced these 50 hours ago, it seems the insulation can’t handle the temperature. What wire is good for this engine? I cut back all wires and will test tomorrow. Even if it is not missing I think I need to find a more suitable wire. 

    40118_2_IMG_4319.jpeg (You do not have access to download this file.)

    Walt

    my blog; waltsrv12.com


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