werxcv01
Well Known Member
Returning from AirVenture, I had some mag trouble so left my -8 with St. Charles Flying Service at KSET and rented a car for the rest of the trip to Mississippi. I will admit to not remembering which key position selected which mag. I’ve had the aircraft for 2 years now (O-360, an aviation mag powering the aviation plugs on the bottom cylinders and an E-Mag powering the automotive plugs on the top cylinders) and every time I checked the magnetos it always seemed that the first key turn to the left resulted in less of an RPM drop than the second key turn to the left, so I had in my mind that the first key turn was the E-Mag. I had overnighted in Davenport Iowa on Saturday night after leaving Oshkosh in the mad rush to depart Saturday morning when the field finally went to marginal VFR. I had the airplane hangared at Davenport so I could depart early Sunday morning and not worry about a wet cover. On run up, I had low rpm of about 1450 on one mag. I assumed that there was lead buildup on the spark plugs so I went through the process of burning it off. That took a few times but I was finally able to get two consecutive good mag checks, so I took off. Cruising at 8500 feet I noticed an RPM drop of about 150. I went to full rich and checked carb heat, but I did not think about checking the magnetos. The RPM returned to normal but I had already started my descent to St. Charles. The Director of Maintenance happened to be there that Sunday morning so he cleaned, tested and gapped the lower aviation plugs but they all checked out fine. He then opened the front of the aviation magneto and we found a trace of oil in the case. Thinking we had found the problem, he had the magneto shipped off to be checked out. The magneto had last had the 500 hour inspection about 125 hours earlier, but they did find a missing tooth on one of the gears and the condenser was old and needed replacing. However once it was reinstalled, the engine still ran rough, apparently because of the E-Mag. Troubleshooting that, they determined that two of the automotive ignition cables were bad. Once they replaced those they determined that possibly the coil was bad. They replaced that but it is still not running smoothly. As of today they are sending the E-Mag back for the factory to look at. All the time that they were diagnosing the E-Mag they were talking to the company service rep, who suggested that the bad ignition cables could have caused a problem with the magneto.
This magneto was rebuilt less than 30 hours previously because I made the mistake of turning on the master while a battery charger was hooked to the Odyssey battery. There is another thread here covering that.
I am now wondering if I should consider a different magneto. I had previously thought to replace the aviation magneto with a second E-Mag, but now I am not so sure.
Any thoughts on why the bad ignition cable would have affected the magneto? Any suggestions for the most efficient way to get my airplane flying dependably?
This magneto was rebuilt less than 30 hours previously because I made the mistake of turning on the master while a battery charger was hooked to the Odyssey battery. There is another thread here covering that.
I am now wondering if I should consider a different magneto. I had previously thought to replace the aviation magneto with a second E-Mag, but now I am not so sure.
Any thoughts on why the bad ignition cable would have affected the magneto? Any suggestions for the most efficient way to get my airplane flying dependably?