Another pmag question

[danny]

My motor was acting funny when throttled back in the pattern. No popping or weird drama, just an uneven idle. It's never done this before. I ended removing the mag and discovered a very small but perceptible amt of play in the shaft. Book says as much as .030" (?) is ok. Danny says no. Asking the brain trust what your thoughts are.
Thanks
danny

 

[lr172]

Very common problem with pmags. the play messes with the internal sensor gap and you have issues. Needs to be sent in for repair. Be sure your sitting when looking at the new repair rates. have no idea what amount of slop in the bearing is allowed, but if it has already translated to poor performance then the spec doesn't matter.

Are you sure ignition is the source of the rough idle?

 

[mfleming]

My motor was acting funny when throttled back in the pattern. No popping or weird drama, just an uneven idle. It's never done this before. I ended removing the mag and discovered a very small but perceptible amt of play in the shaft. Book says as much as .030" (?) is ok. Danny says no. Asking the brain trust what your thoughts are.
Thanks
danny

When I called E-Mag, they said any discernible play was unacceptable and needed to be sent in for a rebuild. My P-Mag has been at the Hartzel rebuild shop since May 7th for rebuild.

Edit: 250 hours on my P-mag

 

[danny]

When I called E-Mag, they said any discernible play was unacceptable and needed to be sent in for a rebuild. My P-Mag has been at the Hartzel rebuild shop since May 7th for rebuild.

Edit: 250 hours on my P-mag

The .030" is from the troubleshooting guide. 105 hours. We're you quoted a $$ amount? Really poor timing here. The airport is going to close for a couple of months starting in July so I was hoping for a bit of flying before that. Did you have any symptoms or were you just doing your annual? Pmag went from hero to zero overnight.
Thanks
danny

 

[danny]

Very common problem with pmags. the play messes with the internal sensor gap and you have issues. Needs to be sent in for repair. Be sure your sitting when looking at the new repair rates. have no idea what amount of slop in the bearing is allowed, but if it has already translated to poor performance then the spec doesn't matter.

Are you sure ignition is the source of the rough idle?

99.9% sure. The T/S guide says .030" is max. I don't like any amount. It was uneven and almost died on the ground without giving it a little stick. Checked plugs maybe 7 hours ago. My motor doesn't run rich. Filter is good. All the other stuff is good. I have an engine monitor and will download later. Mag is an obvious potential issue. Hopefully the only one. And, yes, will be sitting maybe with an adult beverage to cushion the blow.
danny

 

[Mikeyb]

Can’t find any quantitative reference to the end play other than “excessive play” in the current 114 manual or troubleshooting sections

 

[mfleming]

Can’t find any quantitative reference to the end play other than “excessive play” in the current 114 manual or troubleshooting sections

Me neither but the factory told me any play you can feel when aggressively wiggling the shaft indicates the need for overhaul.

 

[danny]

Can’t find any quantitative reference to the end play other than “excessive play” in the current 114 manual or troubleshooting sections

"You might detect (feel or hear) a small outward shift in the position of the shaft. The expected movement is rather small - 0.030” or less." from the trouble shooting tips on the website.
dk

 

[fixnflyguy]

My neighbor just went through P-mag overhauls after some hot start issues that caused backfiring through the induction system. He sent both off for overhaul, and the problem seems to be gone. Seemed like about 3 weeks to a month for the overhaul. Yes, it was expensive. Slop in the bearings was mentioned, but I don't know details..He may chime in if he is watching this thread. I'm old school and just run good old Bendix mags...seems like P-mags are having issues, but I don't have deep knowledge of them.