Mag Stranded me again

[nfonville]

Last February, I had a mag cause the engine to run rough and was stranded in Knoxville. Found that they had 650+ hours since overhaul.  Easiest option was replacement. Then replaced the other at home a few days later.  So two new mags about 150 hours ago.

Today, I'm stranded in Lubbock TX with a dead mag.  Turn the switch to L and engine dies. Turn to R and runs ok.  The mag check was good on the ground when I departed.  At 5000 or so, plane shook and begin to vibrate.  Turned to L and it was dead. Back to both and returned to airport.

Besides a bad ignition switch or mag, what else could it be?

Thanks...

[LANCECASPER]

I am betting on a bad mag. New slick mags have a very bad reputation out of the box- lack of quality control by Champion. No one that I know replaces two Slick mags with new ones out of the box at the same time. You are tempting the Slick Magneto gods.

A lot of people even alternate 500 hour inspections, so at least you have one known good mag. I replaced my right mag in 2015 and in 2018 preemptively sent off the left one for the 500 hour inspection early just to make sure. When I verified that it was running well after I got it back than I changed the ignition harness which was 25 years old. I had thought about changing the harness while the mag was sent off for inspection  but then realized that if it came back it didn't run well I wouldn't know for sure if it was the harness or the mag.

[RLCarter]

could be a grounded "P" lead

[nfonville]

2 minutes ago, RLCarter said:

could be a grounded "P" lead

How does one do a quick test of that?

[nfonville]

7 minutes ago, LANCECASPER said:

I am betting on a bad mag. New slick mags have a very bad reputation out of the box- lack of quality control by Champion. No one that I know replaces two Slick mags with new ones out of the box at the same time. You are tempting the Slick Magneto gods.

A lot of people even alternate 500 hours inspections, so at least you have one known good mag. I replaced my right mag in 2015 and in 2018 preemptively sent off the left one for the 500 hour inspection early just to make sure. When I verified that it was running well after I got it back than I changed the ignition harness which was 25 years old. I had thought about changing the harness while the mag was sent off for inspection  but then realized that if it came back it didn't run well I wouldn't know for sure if it was the harness or the mag.

I have never heard this so it's good to know.  DMax replaced the second one right after I have the one done in Knoxville.  I wish he would have said something about the failure rate because I would have waited for the overhaul and not done a new replacement.

Edited January 26, 2019 by nfonville

[LANCECASPER]

Also, I've thought about this,  for what you get for the cores sending them back it might be worth it to keep them and have them ready to send off for inspection or overhaul.

[RLCarter]

22 minutes ago, nfonville said:

How does one do a quick test of that?

removing the "P" lead from the Mag makes the Mag "HOT". I remove the "P" lead at the Mag and place a temp. jumper from the P-lead to ground on BOTH mags, then is safe to test the leads

[nfonville]

22 minutes ago, LANCECASPER said:

Also, I've thought about this,  for what you get for the cores sending them back it might be worth it to keep them and have them ready to send off for inspection or overhaul.

Wish I would have know

[RLCarter]

Also I was chasing down an issue on a rough running engine only to find that the P-leads were reversed, so the rough running on left only Mag turned out to be a cracked distributor block in the RIGHT mag.

remember to treat ALL mags as HOT, unless its off the plane and on the bench completely disassembled and even then the condenser can still bite you if it hasn't bled off its charge 

[Shadrach]

So left mag is dead, but the engine still starts normally? I’m leaning towards ignition switch if the engine starts normally given the impulse coupling is on the left mag.  Do you have an engine monitor? Do you get an EGT spike going from both to right?

Edited January 26, 2019 by Shadrach

[N201MKTurbo]

That happened to me last month on the way to Dallas. Stopped in Odessa and the great folks there had me fully functional in lassthan 2 hours for an amazingly cheap price.

[nfonville]

OK update:  turns out the right mag p lead is shorted or the ignition switch is bad.  Removed the P lead from the right mag and everything runs normal just won't shut off in the "Off" position.  Learned that it would not start should the left mag been bad according to the mechanic.  I did not look for the EGT spike in flight but will pull JPI data and look for it. CHT and EGT numbers were not out of normal range but could have been higher and just not noticed.

[jaylw314]

3 hours ago, LANCECASPER said:

You are tempting the Slick Magneto gods.

My condolences to the OP, but that quote made me laugh!

[LANCECASPER]

13 minutes ago, nfonville said:

Learned that it would not start should the left mag been bad according to the mechanic.  

Good point - the left mag is the impulse mag. It needs that to start. Maybe the ignition switch.

[carusoam]

All stuff you can know by reading MS...

Another thing you can learn...  is how to leave the ignition switch when you know you have a dead mag...

There is a good reason why you don’t leave it on Both...

None of this stuff is ever taught during flight school 101.  It barely gets mentioned in the 10 day instrument training... or the written exam...

The search function is your friend...  or just hang around here more often...

How would you expect to learn that one manufacturer of mags has been building crap for decades, nobody replaces mags in pairs, unless needed... and one thing that kills mags is the environment that they generate... ozone... plastic gears in O3 turn brittle, a broken gear tooth  in the mag can be a problem...

After all that, did you consider electronic mags at all?

Other things you can familiarize yourself with...

• P wires and their connections... grounding is important, not grounding can be like playing with a loaded gun...
• OH of the ignition switch... (yes, people do that too)

PP thoughts only, all stuff I read around here...

Best regards,

-a-

[Shadrach]

44 minutes ago, LANCECASPER said:

Good point - the left mag is the impulse mag. It needs that to start. Maybe the ignition switch.

Echo...echo...echo.....

[LANCECASPER]

1 minute ago, Shadrach said:

Echo...echo...echo.....

lol, oops, didn't see your post

Great minds think alike . . . but what does that have to do with us?

[alextstone]

7 hours ago, carusoam said:

After all that, did you consider electronic mags at all?

-a-

@carusoam, do you have electronic mag(s)? Anyone else? 

Are they more reliable in reality?  Do they improve performance or efficiency as the manufacturer claims?  Or, are they an expensive alternative with no "proven" benefit?

Alex

[Shadrach]

1 hour ago, alextstone said:

@carusoam, do you have electronic mag(s)? Anyone else? 

Are they more reliable in reality?  Do they improve performance or efficiency as the manufacturer claims?  Or, are they an expensive alternative with no "proven" benefit?

Alex

Having another 10 degrees of advance would certainly improve the efficiency and power of a normally aspirated engine at altitude. Turbo, not so much. 

Edited January 26, 2019 by Shadrach

[nfonville]

I have been thinking through what I learned last night and maybe I'm now confused.

Symptoms: Plane runs rough. Turn mag switch to L and engine dies.

Action taken: Remove Left P-lead.  Plane very hard to start and also dies if mag switch in L position.

Action taken: Replace Left P-lead, remove Right P lead. Plane starts normally. Engine runs in all switch positions including "Off".

Question is: With the right p lead off are both mags functional?  During a run up, putting the switch in the R or Off position should kill the Left mag and get a RPM drop?

Also, If I don't get a mag drop does that mean the Left mag is really bad?

Forget legalities of this question: Assuming I get a mag drop, with the current configuration are both mags operating and ok to fly to home base 1.5 hours away?

 

Edited January 26, 2019 by nfonville

[carusoam]

Is the right p lead on the right side of the engine?

I can get confused... so make sure you know which is which...

taking both p leads off is like running with the switch in the both position...

 

 

Alex, I do not have electronic mags, but I sense the days are coming...

The ability to discuss them openly, the plusses and the minuses... will help.

 

Pp thoughts...

Best regards,

-a-

[N201MKTurbo]

When you remove a P lead you cannot turn the mag off. If you remove the P lead from the good mag it will look like everything is working great because you can’t turn off the good mag.

[skykrawler]

When the switch is in the L position the right mag is grounded and the engine is running on the left mag only.  Vise-versa for the R switch position.  From your last post it seems like your p-leads may be reversed.   From your last post is sounds like both mags are operating.   Disconnect p-leads and use an ohm meter to test between each p-lead and ground.   Both p-leads should show OPEN in the both position  and CONTINUITY for the opposite p-lead for the R and L switch position.

It's important to have the p-leads attached to the correct mag for diagnosing cylinder/ignition problems with the engine monitor.

[nfonville]

So I removed the p-leads from both mags and tested the wiring.    All appears to be correct and work as expected.  I guess in the end it will be 100 hour failure of the left mag.

Thanks for the input from everyone.

 

[nfonville]

Does anyone have the part number for the Left mag?