Ignition Leads

My aircraft ("Super -7") has pumped up engine and dual "P" mags. 350 hours. I run NGK BR9ES plugs. Lately, aircraft runs great at lower altitudes, but at 9-11,000 feet, cannot lean to peak as usual without roughness on both mags, no discernable pattern on the engine monitor, only smooth when quite rich. I wrung out the ignition harness, all wires looked cosmetically new, but 4 out of 8 were either open or high resistance. I have a new harness on the way, hope that solves the problem. Anybody have similar issue?
DAR Gary

Check out Vic

Hi Gary,

Vic S. Just put out a video on this subject of spark plugs on YouTube 23 hours ago. Sounds like the open plugs may be your issue. You can find the Video under his Base Leg Aviation channel. Titled: Overheating Rotax, Battery Terminals, Black Friday book sale.

I am running the same NKG plugs with no issues.

Good luck tracking down your issue.


Mark

missing

Thanks for the input. Brad at P-Mag has been a fountain of information, and once I understood exactly how the P Mag operated, I know how to troubleshoot for the issue. I experimented with plug gaps at .020 all the way to .035, no change, but the either high resistance or totally open test of the leads was conclusive. While I was at it, I rotated the Mags where I could see the *&$$%% LED, and life is good!

Regards,

DAR Gary

termination likely

Unless the wire has been sharply bent, nicked or has the insulation otherwise damaged, I've found that it's normally the wire right at the terminal that is at fault. If you pull the boot back on your faulty lead (assuming NGK, MSD or other automotive style wire), and then stick your multimeter probe in between the center wire and middle insulation (often a thick white silicon insulator), you might find that your wires are still good and that the likely cause is the copper wire, which is a tightly wound around the inner core, is nicked or broken near where it was initially stripped.

If you have sufficient length, you can often cut off the bad end right a the base of the terminal, strip and re-crimp on a new terminal, saving an otherwise good wire.

Seeing that you've already bought new wires, an experiment would be to cut the ends off of the bad wire, strip and measure to verify if that was the problem.