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Ignition system issues and a couple other strange scenarios… that’s what we’ve got for today.
Also, if you have not seen Dean’s safety wiring tutorial course, be sure to check out the details here:
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In today’s episode, we talk about three different airplanes, and the issues each one had with their ignition system. Perhaps if you encounter something similar in the future, this information will be helpful in troubleshooting your airplane’s situation.
Before getting into those issues, we also talk about a couple out-of-the-ordinary situations that might be worth mentioning. Here they are:
- An ACK E-01 ELT that would not test properly. It turns out that one of the eight Duracell “D” batteries was corroded internally causing it to show no voltage.
- An intermittent master electrical switch. The switch contacts had burnt spots on them.
Now for the ignition system issues:
- A Piper Cherokee 235: During the mag timing check, I discovered the mags were “hot” even with the ignition switch in the “off” position. The switch was not able to ground properly because the broken portions of the shielding ground wiring on the P-leads. A new ground wire from the ground terminal of the ignition switch to the airframe, fixed this problem.
- A Mooney M20J: A transient airplane at SHD, that ran rough when the right mag was selected. After some head-scratching trouble shooting, we discovered the P-leads in the dual magneto were swapped… they were installed in the wrong positions. After installing the P-leads in the correct positions and replacing the #4 bottom spark plug due to a cracked ceramic, the engine ran just fine, and they were on their way again. Tom McFadden is the owner of this airplane… a super friendly guy I might add. He had an interesting business where he provides a service to digitize aircraft maintenance records. You can find information at MyAvBook.com
- A Cessna 172RG: The pilot / owner reported “Repair left mag (no RPM drop.)” It turns out the right mag P-lead was broken, causing no RPM drop when left mag was selected. This was because there was no capability to ground the right mag, since the P-lead was broken.
If you know of any interesting ignition system stories, let me know and maybe we can include some of those in a future episode.
Happy troubleshooting, and safe flying!
recently i replaced overhauled magneto to my rv9 aircraft. during ground run found that when the ignition switch at Both engine run smooth.select to L no RPM drops or no response at all when selrect R engine dies.checked the P leads very good .anywhere i replaced P leads and ignition switch, still im having the same problem . please some one can guide me next steps.
If you select R mag and the engine dies, it would seem the R mag is bad. Or, the P-leads could be swapped and the L mag is bad. You could also swap the P-leads and see what happens. Which mag did you replace? Did it work at all after replacement? Let me know.
where are the mags typically ground faulted? I am having this problem, engine quits on right mag
If the engine quits when you select one mag, it’s usually either a bad mag, or a worn P-lead wire that is shorting to ground somewhere, often near the magneto. You might be able to do some troubleshooting by swapping the P-leads left and right. Let me know how it turns out.