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  #21  
Old 01-27-2018, 09:52 PM
Canadian_JOY Canadian_JOY is offline
 
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Location: Ontario, Canada
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Tim - in conversation last week with Brad Dement of EMag he provided information which contrasts starkly with the suggestion you have made.

To summarize Brad:
- if ONE cylinder is not firing it is likely a bad plug, plug wire or, worst case, coil
- if TWO cylinders are not firing it is likely a loose connection on one of the two outboard wires in the 3-wire connector running from the circuit board to the coils, or a bad circuit board
- Brad was quite clear that a bad coil rarely causes two cylinders not to fire - bad coils typically show up as a single cylinder not firing.

In our case we had Cyl's 1 & 2 not firing (in-flight mag check resulted in terribly rough running and #1 & #2 EGT falling like rocks). Today I replaced the circuit board. Hopefully tomorrow the weather will be good enough for a test flight to confirm whether this fixes it. If not I'm going to be a bit steamed as the circuit board is not cheap at $425 plus shipping.
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  #22  
Old 01-28-2018, 10:40 AM
dweyant dweyant is offline
 
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I'm officially out of ideas.

To recap. When running on the left mag (top spark plugs). My engine runs rough, and the EGT's on #3 drop from about 1400, to about 900.

I have tried.

1 - Pull through test. All four plugs are making sparks
2 - OHM testing the wires.
3 - Replacing all spark plugs
4 - Replacing the coil pack on the left P-Mag
5 - Replacing all spark plug wires on the left P-Mag

The left mag is running rev 40, and has about 340 hours on it in a little less than three years.

I guess I will pull the mag and send it to Emag Air in the morning. Anyone have any other ideas?

-Dan
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Last edited by dweyant : 01-28-2018 at 10:40 AM. Reason: Typos
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  #23  
Old 01-28-2018, 12:41 PM
pilotkms pilotkms is offline
 
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Default Left = Left ???

To state the simple and the obvious > You’re positive the left switch operates the left mag and the right switch operates the right mag ??
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  #24  
Old 01-28-2018, 03:47 PM
dweyant dweyant is offline
 
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Figured it out!

What are the odds that after you have two bad spark plugs in a row?

Greater than 0 apparently.

I was ready to pull the P-Mags and send them back, when my neighbor suggested swapping the spark plugs just to see what would happen. We did it, and the problem moved from #3 to #1.

Replaced the spark plug with another new one, and it runs great now.

Thanks for everyone's help.

-Dan
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  #25  
Old 01-28-2018, 08:51 PM
Canadian_JOY Canadian_JOY is offline
 
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Glad to hear you found the source of trouble, Dan.

As a follow-up to my earlier posts, today I flew with the new circuit board in our P-Mag. Engine ran like a top. Failure to fire #1 & #2 plugs was indeed a problem with the circuit board.
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  #26  
Old 01-29-2018, 07:01 AM
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Toobuilder Toobuilder is offline
 
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Quote:
Originally Posted by dweyant View Post
Figured it out!

What are the odds that after you have two bad spark plugs in a row?

Greater than 0 apparently.

I was ready to pull the P-Mags and send them back, when my neighbor suggested swapping the spark plugs just to see what would happen. We did it, and the problem moved from #3 to #1.

Replaced the spark plug with another new one, and it runs great now.

Thanks for everyone's help.

-Dan
Did you ohm check the last batch of new plugs, and if not, did you ohm the most recent bad one? If so, what was the reading?
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  #27  
Old 01-29-2018, 11:00 PM
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RV10inOz RV10inOz is offline
 
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Original post DATA
Quote:
Might be unrelated, but going back and looking at #2 CHT's they usually run at about 340 in cruise, the last few flights they have been mid 320's.

In Instrument flying you learn to trust your instruments. The EMS is no different. The data was telling the story......

Quote:
Originally Posted by RV10inOz View Post
The CHT dropping is a sign of one plug not firing. You should also see an elevated EGT from normal (whatever normal would be for that probe) of something like an extra 60-90dF.

As others have noted, corrosion wire faults or just a flakey plug from new. It happens.

We have seen this on magneto's, what is the chances of two identical faults in overhauled mags? Not =0 either it seems.

Glad you found a cheap problem.
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  #28  
Old 01-30-2018, 08:48 AM
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ColoRv ColoRv is offline
 
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EI Commander is worth its weight when it comes to diagnosing Pmags. My pmags have been back to Brad twice in 4 years...both times because the EI Commander noticed something going south before it affected the engine enough to cause me any real issues. Both times Brad found and fixed the issue quickly because I could tell him exactly what the symptom was and which cylinder it was affecting rather than "the engine is running rough".
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  #29  
Old 02-09-2018, 06:03 PM
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N941WR N941WR is offline
 
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Quote:
Originally Posted by ColoRv View Post
EI Commander is worth its weight when it comes to diagnosing Pmags. My pmags have been back to Brad twice in 4 years...both times because the EI Commander noticed something going south before it affected the engine enough to cause me any real issues. Both times Brad found and fixed the issue quickly because I could tell him exactly what the symptom was and which cylinder it was affecting rather than "the engine is running rough".
Thanks, that is nice to hear.
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Last edited by N941WR : 02-09-2018 at 06:07 PM.
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  #30  
Old 02-10-2018, 02:38 AM
jakej jakej is offline
 
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Location: Adelaide, Australia
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What I find is really worrying is the original subject said P-Mag issues when it was clearly not, really unfair to any manufacturer when an issue is not with their product - it's about time some of us think before 'pointing the finger'.
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