Q-talk 104 - Electronic Ignition Troubleshooting
- Category: Q-Talk Articles
- Published: Wednesday, 23 December 2009 16:24
- Written by Terrence O'Neill
- Hits: 1454
Former co-owner of N189SM Dragonfly Mk II. (Looking for a nice tri-gear Q2 or Dragonfly)
An item of interest to those with electronic ignition. Mine is on a Continental A-80. I have a dual early model LSE Plasma CDI installation with about 200 hours on it. Recently I experienced a little RPM-drop, like 25 to 50, when checking the LSE CDIs. Starting was always immediate, and power on takeoff and flight was fine.
But this slight RPM drop was unnatural and it worried me. Normally the tach doesn't move when checking the CDIs. So we did some ground run-ups. It gradually got worse. We tried leaning. No change. Not the carburetor. We put in new sparkplugs. No change. We checked the spark wiring. No change. At one point on a ground run-up at around 2000 or so RPM, the engine actually cut out and backfired a little, but ran pretty smooth at idle. We began trying to isolate the RPM drop at various RPM. We swapped the four coils around, left to right, front, then back. No change. I have the Hall Effect sensors in the magneto holes, so we swapped the connections and one got worse, but on a second check, it ran normally! Veiy confusing.
I called Klaus. He has this all in his head. I explained all that we did, and he suggested a few things we'd already done. Then he suggested we clean the 9-pin connectors that plug into the Hall Effect modules. My co-checker is into electronics, and he did that. He noticed a slight brownish haze on the little connectors and said "Corrosion!" He sprayed it with electrical cleaner, wiped it off, and we ran it up. Ran good. We flew it. It worked like new. He then flew it from here to Tucson, AZ and the engine ran flawlessly. Now we're looking for some way to keep moisture off of and out of the connectors. Maybe the gold connectors the radio control guys use?
Anyway, hopefully this experience will help correct or avoid problems for others.
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