bruceh
Well Known Member
A bit of background:
My RV-9A has dual P-mags. Airplane is approaching 1000 hours of trouble free electronic ignition usage.
I did my condition inspection last month (June 2022) which involves inspecting the bearings on the P-mags for "excessive play". Mine both had what I would call excessive play (one had a lot, the other was minimal, but still was moving around the axis of the bearing).
I sent both of them back to E-mag for the flat-rate checkup. Got them back, installed them as usual - set the timing, reset the proper advance curve, and all was well again.
I flew about an hour and had no issues, then before another local flight I had a
mag-check failure and the internal generator was also not powering the ignition properly below 1000 RPMS. Plug wires were checked and had good resistance readings. Sparkplugs are new NGK BR8ES. The EGT's/CHT's didn't point to any particular cylinder going cold, just ran really rough and dropped from 1700 RPM to 1200-1400 RPM during the mag check.
I checked the connections, wires and timing which all looked good.
I did some more run ups and was unable to get the internal generator test to pass. I pulled both P-mags off and swapped them. Retimed again and then did more run ups. This time the problem moved sides, so I knew it was definitely the one P-mag.
I sent this off to E-mag again, and they confirmed there was an electronic issue. They swapped out the internals and sent it back at no charge (great service by the way). I reinstalled this P-mag and went through all of the usual timing steps. I went flying on Saturday and everything was working great again. No issues with the mag check or the internal generator tests.
Today I flew up to Corona to pick up some items from Aircraft Spruce. The departure run up was perfect with no issues. I landed, got my will-call order and had some breakfast at the Cafe, I then fired up the airplane for the short trip home.
The engine failed the mag check. When I selected the Left P-mag (this one is not the one that was recently re-repaired), the engine would back fire and quit if just left on the left side. I got the airplane over to the maintenance shop on the field and took off the cowling. I was able to talk with Brad at E-mag and he gave me a number of suggestions. The first one was to confirm that the timing was still set.
I borrowed a mirror (and also used my cellphone camera to video the LED on the Left P-mag) to see if the LED at TDC was Green like the other P-mag. It was steady Red all the way through 720 degrees of prop rotation.
I set the timing on the left P-mag and it went back to being in sync with the other P-mag. Both LED's flash green at TDC.
Very strange!
I did another run up and mag check and all was good again. I reinstalled the cowling and did another extensive set up run ups before departing back to Ramona. No issues in the flight home.
Now I'm trying to figure out what could have caused this problem. Reading other threads on P-mags losing timing call out some potential culprits. I'm running the most current Firmware version #41, so it should have the latest fix for losing timing on powering up during the engine running. I don't use a trickle charger, so that isn't pulsing any of the electronics. I have blast tubes on the P-mags and have not had any overheating issues in the past (but it has been hot lately here). The EIC display showed both P-mags in sync and advanced at the same curve. I'm running the recommended timing for my IO-320 and I've confirmed that both P-mags have the same timing curves set.
Oshkosh awaits and I'm wondering if I can depend on these to get me there and back without issues.
What else should I investigate?
Brad suggested bypassing the EIC and just putting in the jumper for the A curve timing. He also suggested testing without the ground wire from the key switch in place to see if there might be a grounding issue inside the key switch that might be disabling the P-mag.
My RV-9A has dual P-mags. Airplane is approaching 1000 hours of trouble free electronic ignition usage.
I did my condition inspection last month (June 2022) which involves inspecting the bearings on the P-mags for "excessive play". Mine both had what I would call excessive play (one had a lot, the other was minimal, but still was moving around the axis of the bearing).
I sent both of them back to E-mag for the flat-rate checkup. Got them back, installed them as usual - set the timing, reset the proper advance curve, and all was well again.
I flew about an hour and had no issues, then before another local flight I had a
mag-check failure and the internal generator was also not powering the ignition properly below 1000 RPMS. Plug wires were checked and had good resistance readings. Sparkplugs are new NGK BR8ES. The EGT's/CHT's didn't point to any particular cylinder going cold, just ran really rough and dropped from 1700 RPM to 1200-1400 RPM during the mag check.
I checked the connections, wires and timing which all looked good.
I did some more run ups and was unable to get the internal generator test to pass. I pulled both P-mags off and swapped them. Retimed again and then did more run ups. This time the problem moved sides, so I knew it was definitely the one P-mag.
I sent this off to E-mag again, and they confirmed there was an electronic issue. They swapped out the internals and sent it back at no charge (great service by the way). I reinstalled this P-mag and went through all of the usual timing steps. I went flying on Saturday and everything was working great again. No issues with the mag check or the internal generator tests.
Today I flew up to Corona to pick up some items from Aircraft Spruce. The departure run up was perfect with no issues. I landed, got my will-call order and had some breakfast at the Cafe, I then fired up the airplane for the short trip home.
The engine failed the mag check. When I selected the Left P-mag (this one is not the one that was recently re-repaired), the engine would back fire and quit if just left on the left side. I got the airplane over to the maintenance shop on the field and took off the cowling. I was able to talk with Brad at E-mag and he gave me a number of suggestions. The first one was to confirm that the timing was still set.
I borrowed a mirror (and also used my cellphone camera to video the LED on the Left P-mag) to see if the LED at TDC was Green like the other P-mag. It was steady Red all the way through 720 degrees of prop rotation.
I set the timing on the left P-mag and it went back to being in sync with the other P-mag. Both LED's flash green at TDC.
Very strange!
I did another run up and mag check and all was good again. I reinstalled the cowling and did another extensive set up run ups before departing back to Ramona. No issues in the flight home.
Now I'm trying to figure out what could have caused this problem. Reading other threads on P-mags losing timing call out some potential culprits. I'm running the most current Firmware version #41, so it should have the latest fix for losing timing on powering up during the engine running. I don't use a trickle charger, so that isn't pulsing any of the electronics. I have blast tubes on the P-mags and have not had any overheating issues in the past (but it has been hot lately here). The EIC display showed both P-mags in sync and advanced at the same curve. I'm running the recommended timing for my IO-320 and I've confirmed that both P-mags have the same timing curves set.
Oshkosh awaits and I'm wondering if I can depend on these to get me there and back without issues.
What else should I investigate?
Brad suggested bypassing the EIC and just putting in the jumper for the A curve timing. He also suggested testing without the ground wire from the key switch in place to see if there might be a grounding issue inside the key switch that might be disabling the P-mag.