I had a half coil failure on my 11 year old Electroair EI. It would fire only one of the two wires connected to the "B" coil. Since it fires on every up stroke (lost spark system fires on the exhaust as well as the power stroke) I switched cylinder 3 and 4 wires as a test: the bad firing followed to the opposite cylinder.
All of this was easily observable on the engine analyzer. If the magneto was operating and the EI (so that both systems were on) the indication was a 300F increase in EGT and a 50 decrease on CHT. If you run it only on the bad performing EI: both EGT/CHT would go cold in the 250F or less on the bad coil post.
I was lead to believe a Delco D555 automotive coil would be a direct replacement however the internal clips would not accept the 2 flat brass prongs or let the coil slide on. This may be a change by Delco of the internal clips over the years.
The equivalent MasterPro coil sold at O'reilley Auto parts PN#2-5192 or E51 will slide on the prongs easily.
That is where I'm at right now. I have not run it yet as the wind was blowing last night too hard to try to open the hangar.
Last edited by Boyd Birchler : 02-12-2015 at 12:16 PM.