Intermittent issues with left mag

[redbaron1982]

For the last months (3 or 4) I have been having intermittent issues with the left mag.

The issues are grouped into either in-flight mag check failure or runup mag check failure. Every time the issue was "fixed" by removing/cleaning/gapping the spark plugs. The issues are always engine running rough, never complete loss of power.

Yesterday, by recommendation of Savvy, I replaced all spark plugs (they had roughly 400 hours). I put fine wires on the bottom and massive ones on the top holes. I did a run up and again, left mag was not good, with a 200 rpm drop. 

Right mag is always ok.

I have the dual mag Lycoming IO360-A3B6D.

Any thoughts? Could this be due to bad leads or the mag itself? The mags were overhauled 40 hours ago by Kelly.

[Hank]

Leaning aggressively on the ground will significantly reduce lead build up. 

When I had this problem, it turned out to be a single bad lead from the magneto to one cylinder. The one-wire replacement kit was about 80% the price of a complete ignition harness, with 8 leads and both magneto caps. My harness had ~100 hours on it at the time, so I replaced the one wire then did the timing. (Actually my IA did it, after driving 30 minutes to my hangar.)

[EricJ]

Recently somebody had trouble with plugs failing the resistance test.    That might be something to check.

[MikeOH]

5 minutes ago, EricJ said:

Recently somebody had trouble with plugs failing the resistance test.    That might be something to check.

I think he said he replaced all the plugs…would seem pretty unlikely the new set was bad, too.

[redbaron1982]

I want to clarify, spark plugs are all brand new. I installed them yesterday at 6pm, did the runup at 620pm... left mag failed after the engine was fired up. So no fouling, lead build-up, or anything.

I lean toward either a bad lead(s) or the mag itself.

[EricJ]

2 minutes ago, redbaron1982 said:

I want to clarify, spark plugs are all brand new. I installed them yesterday at 6pm, did the runup at 620pm... left mag failed after the engine was fired up. So no fouling, lead build-up, or anything.

I lean toward either a bad lead(s) or the mag itself.

If you pull the plugs again, I'd still check.   I seem to recall somebody had a bad batch of new ones and the fix was to replace the plugs again.   If they're new, you can likely return faulty ones if they don't pass a resistance test.

Otherwise, the usual things apply, like removing the p-leads one at a time to make sure the switch or a p-lead isn't faulty, checking timing, etc.  40 hours on the mag is about the right time to re-check timing, anyway, to account for wear-in of the cam followers on the points.    If you have access to a cable tester for the ignition leads, that's a good check to make as well.

[Fly Boomer]

31 minutes ago, redbaron1982 said:

I want to clarify, spark plugs are all brand new. I installed them yesterday at 6pm, did the runup at 620pm... left mag failed after the engine was fired up. So no fouling, lead build-up, or anything.

I lean toward either a bad lead(s) or the mag itself.

Anything can fail at any time -- including before you install it.

[MooneyMitch]

It's so unfortunate we're flying around such out dated ignition stuff.  I'm trying to remember the last time one of my autos engines quite running, stumbled, ............... or the ignition system failed, etc.  I can't recall!

[Shadrach]

Is it the same cylinder? IO360s don’t typically foul from lead at idle no matter where the mixture is set. Our engine was idled and taxied at full rich for the first 30 years of its life and suffered no issues from lead fouling.

I am inclined to believe there is an issue with the harness if it’s always the same cylinder causing trouble. 

[EricJ]

8 minutes ago, MooneyMitch said:

It's so unfortunate we're flying around such out dated ignition stuff.  I'm trying to remember the last time one of my autos engines quite running, stumbled, ............... or the ignition system failed, etc.  I can't recall!

They do when they're forty years old. 

Cars are great for about ten or twenty years if you're lucky, then the parts dance starts to happen.   I have a Ranger that is 23 years old and the injectors and ignition have been gone through a couple times.   My BMW was 25 years old and, while generally very bulletproof, would need a COP (coil) or something from time to time.

I'm a fan of the modern tech, though, especially the diagnostic capabilities.   It's a bummer that the aviation market is not big enough to have made the improved tech mainstream for us.    There's a lot to be said for simpler systems, too, though, especially that'll run when the electrical system fails completely. 
 

[dzeleski]

59 minutes ago, redbaron1982 said:

I want to clarify, spark plugs are all brand new. I installed them yesterday at 6pm, did the runup at 620pm... left mag failed after the engine was fired up. So no fouling, lead build-up, or anything.

I lean toward either a bad lead(s) or the mag itself.

What do you mean by it failed? 200RPM drop only means something if you do a mag test with the mixture at full rich.

I dont actually care how much the RPM drops because I do my mag test leaned out. What I do care about is that all of my EGTs see a rise and that the RPM drop between sides is close.

When you do the ground test what is your procedure for doing it?

When you do the inflight test the engine will run rougher, it shouldnt feel like a missing cylinder though. What is your definition of failed for this?

https://resources.savvyaviation.com/in-flight-diagnostics/

Most importantly... Do you have an engine monitor? Can you upload the test data and share the data?

[Shadrach]

5 hours ago, MooneyMitch said:

It's so unfortunate we're flying around such out dated ignition stuff.  I'm trying to remember the last time one of my autos engines quite running, stumbled, ............... or the ignition system failed, etc.  I can't recall!

In over twenty years of flying, I’ve never landed an airplane that was not firing on all cylinders. Over the years, I’ve nursed a number of modern vehicles off the road due to misfires.

There’s no question that the Bendix S200 series magnetos have proven to be quite reliable if not very sophisticated.

[MooneyMitch]

Ok y'all.

[LANCECASPER]

2 hours ago, redbaron1982 said:

For the last months (3 or 4) I have been having intermittent issues with the left mag.

The issues are grouped into either in-flight mag check failure or runup mag check failure. Every time the issue was "fixed" by removing/cleaning/gapping the spark plugs. The issues are always engine running rough, never complete loss of power.

Yesterday, by recommendation of Savvy, I replaced all spark plugs (they had roughly 400 hours). I put fine wires on the bottom and massive ones on the top holes. I did a run up and again, left mag was not good, with a 200 rpm drop. 

Right mag is always ok.

I have the dual mag Lycoming IO360-A3B6D.

Any thoughts? Could this be due to bad leads or the mag itself? The mags were overhauled 40 hours ago by Kelly.

I think we know the problem. Kelly has the worst reputation for mag overhaul of anyone in the business.

 

Aero Accessories of Van Nuys has a great reputation.

[KSMooniac]

I suspect another great overhaul from Kelly...

Do you have a good engine monitor?

[Hank]

18 minutes ago, LANCECASPER said:

I think we know the problem. Kelly has the worst reputation for mag overhaul of anyone in the business.

 

Aero Accessories of Van Nuys has a great reputation.

My brand new Kelly ignition harness was falling apart at annual three years after installation. The IA said i was lucky it didn't fail in flight . . . So he checked two others in his shop, they were falling apart, too. Kelly sent someone over and we all got new harnesses. The next year, I had to replace one lead in my new replacement harness. That stupid wire cost me a weekend at the beach!  

[redbaron1982]

13 minutes ago, KSMooniac said:

I suspect another great overhaul from Kelly...

Do you have a good engine monitor?

I do have.

This is the last in-flight mag check, in the comments I state at what time I start the mag check. https://apps.savvyaviation.com/flights/shared/flight/7536148/a6d61bbe-f393-4d68-8c82-93a8f919fbb2

It seems that the notes are not shared, this are the notes:

At 25:40 I do just one sweep from ROP to LOP. I was operating >70% so I didn't want to do more than one sweep.
At 28:00 minutes I started the mag check at ~75F LOP.
Engine operation on the left mag was not ok, although it was "smooth" it was misfiring a bit. The right mag was ok.
The issue with the left mag has been happening in the last couple of flights. I cleaned/gapped all plugs, but that did not fix it. 
 

 

This was yesterday runup, I couldn't make much out of it: https://apps.savvyaviation.com/flights/shared/flight/7572608/4d5fbacc-345f-4b62-9832-a1ad7135c6c4

Edited November 17, 2023 by redbaron1982

[N201MKTurbo]

You need to check your point gap. I bet your left points have warn to where they are barely opening. All you need to do is reset the point gap and check the internal timing.

[MooneyMitch]

I did have a left mag condenser failure withing 10 hours of my Aero Accessories 500 hour inspection a couple of years ago.  To the credit and fairness to the shop, they replaced the condenser at no charge [no shipping charges either] and they did inform me that they are not required to replace condensers on a 500 hour inspection.  They only test the condensers.

In the future, I would ask them to replace condensers too during the 500 hour process. 

[MikeOH]

Ah, the sweet sound of the archaic term condenser (or, even better, condensator)...much more pleasing than the cold modern term capacitor

The temporal continuity of the term is quite consistent with the design era (epoch?) of our magnetos!

[redbaron1982]

Unrelated but related... what do you guys think about SavvyMx service? After reading Mike Busch books I was expecting top-notch service, and what I'm getting is far from that.

I'm asking about this issue to them, and they insist that this has to be spark fouling. How likely is that is spark fouling that doesn't change after changing all spark plugs with new ones?

[MooneyMitch]

1 hour ago, MikeOH said:

Ah, the sweet sound of the archaic term condenser (or, even better, condensator)...much more pleasing than the cold modern term capacitor

The temporal continuity of the term is quite consistent with the design era (epoch?) of our magnetos!

Gee whiz…… I meant to use the term capacitor (caps), but ……  I didn’t.   The brain is a very interesting organ, especially mine  

[redbaron1982]

1 hour ago, MikeOH said:

Ah, the sweet sound of the archaic term condenser (or, even better, condensator)...much more pleasing than the cold modern term capacitor

The temporal continuity of the term is quite consistent with the design era (epoch?) of our magnetos!

The only capacitor I know is installed in a DeLorean...

(just kidding, condensers became capacitors in my life when I started college)

[EricJ]

1 hour ago, redbaron1982 said:

Unrelated but related... what do you guys think about SavvyMx service? After reading Mike Busch books I was expecting top-notch service, and what I'm getting is far from that.

I'm asking about this issue to them, and they insist that this has to be spark fouling. How likely is that is spark fouling that doesn't change after changing all spark plugs with new ones?

If you are genuinely seeing fouling, then it wouldn't matter how old the plugs are, because the fouling conditions are independent of the age of the plug.   Do you lean during ground operations and keep rpms above about 1000 or so?   If not, that's an easy thing to try to see whether it makes a difference.   I had lead fouling problems until I changed the lower plugs to fine wire and starting operating on the ground this way.    Haven't had an issue since.

Also, lead fouling can often be cured on the ground with a short medium-throttle run with a lean-ish mixture, just enough to get combustion temperatures at the plugs hot enough to vaporize the lead again.

[redbaron1982]

1 minute ago, EricJ said:

If you are genuinely seeing fouling, then it wouldn't matter how old the plugs are, because the fouling conditions are independent of the age of the plug.   Do you lean during ground operations and keep rpms above about 1000 or so?   If not, that's an easy thing to try to see whether it makes a difference.   I had lead fouling problems until I changed the lower plugs to fine wire and starting operating on the ground this way.    Haven't had an issue since.

Also, lead fouling can often be cured on the ground with a short medium-throttle run with a lean-ish mixture, just enough to get combustion temperatures at the plugs hot enough to vaporize the lead again.

Do you think is possible for brand new plugs to foul 5 minutes after install?

I installed the new plugs, start the engine, wait for the oil temp to rise above 75F and then did a runup that was showing a 200rpm drop.