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EMag issue

YellaDawg

YellaDawg

Well Known Member
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150 hours dual emags on IO390 in RV8. started with a "stumble" at low RPMs and not noticeable at higher RPMs, now noticeable. I think my left mag is not running internally. Here is my check:

Grounded the right mag at 1200 rpm, killed internal power on left mag and rpm went to zero and engine quit.
Grounded the left mag at 1200 rpm, killed internal power on right mag and rpm was steady and engine remained running.

My plan is to remove both mags for service. But at 150 hours???

I did a pull test on wires and all are attached, cleaned injectors, no change, plugs have 25 hours on them (issue started before new plugs)

Anything else I should check before I take them off?
 
YellaDawg said:
Grounded the right mag at 1200 rpm, killed internal power on left mag and rpm went to zero and engine quit.
Click to expand...

I'm confident you meant to write "killed external power". If you were conducting the test at typical RPM for the runup pad (1800 or so), then yes, your left internal generator is dead as canned tuna.

YellaDawg said:
My plan is to remove both mags for service. But at 150 hours???
Click to expand...

As noted elsewhere, self-powered is a great sales feature.
 
FwIW- my mags will not supply spark at 1200rpm. I need a bit more for full self exciting capability. Still seems like the left mag internal needs repaired.
 
toolmanmike said:
FwIW- my mags will not supply spark at 1200rpm. I need a bit more for full self exciting capability. Still seems like the left mag internal needs repaired.
Click to expand...
My experince over 20 years with dual pMags. The internal generator will keep the fan running down to ~900 RPM or so. Your’s dies at 1200. Does it still work at 1500?

Working other pMag installs I’ll also note that for whatever reason builders get bent around the axle with their “test” switch, as in wiring mistakes when using a three position toggle switch. Same for using an old school Cessna key switch. I only use an on/off ignition toggle switches and pull-able breaker I suggest verifying wiring as the first step.

Side note - check that you grounded the pMags locally on the engine.

If after verify your symptoms the problem persists, contact eMag for repair.

Carl
 
Last edited:
Sounds like ONE is bad...not sure why you'd want to pull both unless they need the bearing upgrade. Just because one failed at 150 hours doesn't mean the other is about to fail as well.
 
I actually had this happen a few weeks ago. Newly rebuilt engine, new fuel injection and had a stumbling idle at around 800 RPM. It felt like a skip or timing hunting or like a little stumble. A little rumble but only at idle or around 800RPM. High power was completely fine, no issue

My first thought was fuel so chased the idle mixture control thinking that was my issue. However enrichening it would help to mask the issue while leaning would make it worse. Checked all injectors. Checked all the intake and exhaust for leaks and cracks, smoke tested with no luck.

I also have dual p mags
I changed the right mag to a regular slic and the problem still persisted. So put my pmags back on. Figured if it was a timing issue then changing one mag gave me a 50/50 chance of catching it. I didn't want to believe it could be a mag issue because they only had 40-50 hours on them.
What the heck is going on i thought... driving me nutz... I know you can get a rough idle during break in but this doesn't feel right.
I don't have independent switches for my pmags. Just the left right both switch. So my only way to test my internal generator on my pmags is to kill all ship power (master and avionics off) with engine running and RPM above 800 and see if they still run. Then do a mag check. This is what i did. Right mag ran fine. However, left one grounded and shut the plane off immediately but ran fine with ship power on... SO my left internal generator was internally grounded.

Called Hartzell and spoke with Tyler Burrows and sent him the mag. He had it send back within 3-4 days covered under warranty. Said their was a loose wire or a wire inside that either was not done correctly from the factory or had come loose. Either way he fixed and sent it back quick.
Reinstalled Pmag and rumble stopped..

Just my experience.
Hope it helps.
 
Thanks for all of the replies, they are very helpful just to answer a couple of observations, yes I killed external power and the mag would not run at 1200. It does seem to run at higher RPM as in 1700, but I'll run that again just to to confirm, should run at lower RPMs, LIKE ON FINAL. They were installed Oct 2022 as new, plane first flew 3.23 150 hours since then. I will call Hartzell tomorrow, I'll video the events this afternoon so he can get a good look. I want to send both back, just as a precaution. the switches are all toggles, panel built by Advanced so mostly printed circuits on the panel between toggles etc. Again, Thanks for the help, I'll post the end results, fortunately I have a RV14 to take to Oshkosh, with dual P Mags as well. See you there at the beer bash!

YellaDawg
 
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