Plug wire question

[bcg]

I've got a '63 C with an O360-A1D. For a month or so, I've been having some roughness on the right mag off and on, typically leaning it out and running it would clear it up for 7-10 hours but, last week I felt some roughness doing pattern work so I did a taxi back to do another mag check and it was a 300 RPM drop. We tried it 3 times and got it to a 250 RPM drop but, it was still too rough for my comfort so we called it for the day. This afternoon, I headed over to the A&P and we pulled all the plugs, cleaned and gapped them, bomb tested and reinstalled. No change, still a 250 RPM drop on the left side. I'm convinced it's not plugs since we rotated top to bottom so if it were, the issue should have moved to the left.

 

The mags were redone less than 100 hours ago so, I'm hopeful it's just bad wire(s) since that will be a faster fix.

 

My question is this, do plug wires for these come as a premade set like cats or is this something where you take a roll of wire and cut to length to make your own?

 

I'll be back at the shop in the morning to ask the A&P but, I figure someone here knows the answer.

 

If I'm going to have to buy a premade set, is one better than others for this motor? I've seen references to thick wire or massive wire and fine wire as well as slick wire. What's the difference?

 

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[Jpravi8tor]

 

[Hank]

Both options are available. I replaced the entire set a few years ago, then had your exact issue. We tested with a mark on each exhaust pipe near the cylinders, did a run up and three marks burned off. Swapped the two plugs in the marked cylinder, it stayed cold; swapped side to side and the same cylinder stayed cold. 

My IA replaced the individual lead (purchased separately) and it works well now. BUT the kit to replace one wire cost almost as much as a complete new harness . . . .

The old and the new:

The new harness is pre-built, all eight wires and caps for both magnetos, and lots of replacement things (memory farther, what're they called???) to attach the wires and keep them where they belong. Adel clamps! They're white in the second photo. Looking at the old one, they were overdue for replacement, and this isn't the worst part . . .

Be sure to replace the grommets where the upper leads go through the doghouse, and be careful to not pinch the left wires between the battery and the doghouse as shown below:

I went slow and careful, lots of photos before removing things so that I could put the new one in properly; I was prepared to spend a long time, it may have been a relaxed two hours with lots of chatting under supervision. Not much more work than doing the same job on my truck, I needed fewer tools for the Mooney, and Lycoming didn't use unique attachment methods on the back of the engine where its difficult to see (must be a Ford thing, my Chevy truck wasn't like that either).

Now my pretty yellow harness has one wire that's either red or blue, I forget.

P.S.--my new harness was Kelly brand.

[Jpravi8tor]

you can buy single wire kits and complete replacements
https://www.aircraftspruce.com/catalog/eppages/shieldedharness3.php?clickkey=5239

[Marauder]

You didn’t mention checking the resistance of the plugs. I would also do that as well. Some of the plugs had issues with too much resistance causing issues.

The plug wires, as mentioned can be purchased as a set or individually. You will need to make sure the set you purchase matches the plug type. I have fine wire plugs and the end cap is larger.


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[N201MKTurbo]

I would check the point gap and the timing before going for the harness.

[bcg]

You didn’t mention checking the resistance of the plugs. I would also do that as well. Some of the plugs had issues with too much resistance causing issues.

The plug wires, as mentioned can be purchased as a set or individually. You will need to make sure the set you purchase matches the plug type. I have fine wire plugs and the end cap is larger.


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Since the problem didn't move with the plugs, I'm pretty confident they're not the issue.

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[DV8Pilot]

27 minutes ago, N201MKTurbo said:

I would check the point gap and the timing before going for the harness.

This. I had a Bendix mag slip within 65 hrs after a 500 hr service. 

[DV8Pilot]

1 hour ago, bcg said:

 

I've got a '63 C with an O360-A1D. For a month or so, I've been having some roughness on the right mag off and on, typically leaning it out and running it would clear it up for 7-10 hours but, last week I felt some roughness doing pattern work so I did a taxi back to do another mag check and it was a 300 RPM drop. We tried it 3 times and got it to a 250 RPM drop but, it was still too rough for my comfort so we called it for the day. This afternoon, I headed over to the A&P and we pulled all the plugs, cleaned and gapped them, bomb tested and reinstalled. No change, still a 250 RPM drop on the left side. I'm convinced it's not plugs since we rotated top to bottom so if it were, the issue should have moved to the left.

 

The mags were redone less than 100 hours ago so, I'm hopeful it's just bad wire(s) since that will be a faster fix.

 

My question is this, do plug wires for these come as a premade set like cats or is this something where you take a roll of wire and cut to length to make your own?

 

I'll be back at the shop in the morning to ask the A&P but, I figure someone here knows the answer.

 

If I'm going to have to buy a premade set, is one better than others for this motor? I've seen references to thick wire or massive wire and fine wire as well as slick wire. What's the difference?

 

Sent from my Pixel 6a using Tapatalk

 

 

 

If you’re going to replace leads from the mags to the plugs I can’t recommend New Horizons highly enough. I’d just get a new full set if that’s what you need.

 

Do you have a digital engine monitor that has a read out for each EGT? A bad plug can be identified by that egt going cold instead of increasing during the run up mag check. A timing issue will present as all the egts increasing with a significant drop / roughness in rpm. I’d start there and time the mags before replacing leads. If that doesn’t resolve it then I’d go for a full set of leads.

[carusoam]

Please tell us you have an engine monitor….

This will make things really easy to figure out….

 

Things that an engine monitor can find easily….

1) Changes in ignition timing

2) Ignition wires leaking 

3) plugs with increased internal resistance

4) Oil wetting plugs

5) Lead balls collecting in the lower plugs

With an engine monitor… find out which part of the system isn’t working, fix it…

Without an engine monitor… remove and test everything… to find out what isn’t working right… then fix it…

 

Champion spark plugs are still known for their infinite resistance…

Getting a new wire harness is a great idea, if the old one is original to the plane… lots of small parts that may not be working correctly… after so many years of annual inspections…

PP thoughts only, my M20C got a new set of wires from Champion (of all resources…) a relatively low cost upgrade after 40years…

Best regards,

-a-

[bcg]

Please tell us you have an engine monitor….
This will make things really easy to figure out….
 
Things that an engine monitor can find easily….
1) Changes in ignition timing
2) Ignition wires leaking 
3) plugs with increased internal resistance
4) Oil wetting plugs
5) Lead balls collecting in the lower plugs

With an engine monitor… find out which part of the system isn’t working, fix it…
Without an engine monitor… remove and test everything… to find out what isn’t working right… then fix it…
 
Champion spark plugs are still known for their infinite resistance…
Getting a new wire harness is a great idea, if the old one is original to the plane… lots of small parts that may not be working correctly… after so many years of annual inspections…
PP thoughts only, my M20C got a new set of wires from Champion (of all resources…) a relatively low cost upgrade after 40years…
Best regards,
-a-

I planned to put an engine monitor in when I bought the plane. Instead, I've had to replace a failed GPS, starter, generator and now whatever is going on with the ignition system. Hopefully I can get it fairly stable for a while to rebuild the AMU bank to get the engine monitor done. Until then, I've got to do it the hard way.

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[carusoam]

Bummer…

I was so hoping to give an engine monitor lesson!

Start with the plugs… see if any of them are marked with the label ‘Champion’…

There is a method of measuring their resistance…

There is also a method of tossing them in the trash…

Be on the lookout for any missing center electrodes…

If you haven’t been leaning deeply while taxiing… be on the look out for lead balls collected deep in the bottom plugs…

Check the hardware ends of the plug wires… many have been replaced after falling apart over the years…

 

PP thoughts only, not a mechanic…

Best regards,

-a-

[bcg]

9 hours ago, carusoam said:

Bummer…

I was so hoping to give an engine monitor lesson!

Start with the plugs… see if any of them are marked with the label ‘Champion’…

There is a method of measuring their resistance…

There is also a method of tossing them in the trash…

Be on the lookout for any missing center electrodes…

If you haven’t been leaning deeply while taxiing… be on the look out for lead balls collected deep in the bottom plugs…

Check the hardware ends of the plug wires… many have been replaced after falling apart over the years…

 

PP thoughts only, not a mechanic…

Best regards,

-a-

We did a pretty thorough rehab of the plugs yesterday, first a wire wheel on the threads, then a blasting station with coal slag to loosen up any carbon or lead, next to a vibrator that shook out anything that was blasted loose, then the gap was set, back into the blasting station to make sure everything was knocked out and finally a spark test under pressure in what they called the "bomb tester" which was part of the specialized blasting machine.  They all had a strong, clean spark under pressure.  They are all Champion massive wire plugs and all needed the gap closed up a little, it's been about 50 hours since the annual so that's about right for the service interval.  Again, since the problem stayed on the right mag despite the plugs being swapped (left mag plugs reinstalled on right mag and vice versa), I'm pretty confident the plugs are good.

The wires look old, who knows how long they've been in there but, the hardware all looked like it was in pretty good shape on the plug end. 

I have been leaning pretty aggressively on the ground since the first time we had some roughness on the mag check during runup.  We're at 1600 feet so it leans out a lot during taxi.  Honestly, I didn't see a lot of lead on the plugs when we pulled them out, not nearly as much as I was expecting to.  Number 3 had some oil fouling and the most lead, the rest of them were pretty clean.

I'm about to go buy some donuts for the mechanics and head that way, hopefully I'll have some definite answers this morning.  I had not considered timing or the points on the mag as I didn't realize that was something that could be checked without sending them in for overhaul.  It's been a long time since I've worked on something that I could set the timing on so I'm having to remember things that haven't been needed in decades.  Working on this is a lot more pleasant than working on the old VW Bug was though.

[bcg]

11 hours ago, Hank said:

Both options are available. I replaced the entire set a few years ago, then had your exact issue. We tested with a mark on each exhaust pipe near the cylinders, did a run up and three marks burned off. Swapped the two plugs in the marked cylinder, it stayed cold; swapped side to side and the same cylinder stayed cold. 

My IA replaced the individual lead (purchased separately) and it works well now. BUT the kit to replace one wire cost almost as much as a complete new harness . . . .

The old and the new:

The new harness is pre-built, all eight wires and caps for both magnetos, and lots of replacement things (memory farther, what're they called???) to attach the wires and keep them where they belong. Adel clamps! They're white in the second photo. Looking at the old one, they were overdue for replacement, and this isn't the worst part . . .

Be sure to replace the grommets where the upper leads go through the doghouse, and be careful to not pinch the left wires between the battery and the doghouse as shown below:

I went slow and careful, lots of photos before removing things so that I could put the new one in properly; I was prepared to spend a long time, it may have been a relaxed two hours with lots of chatting under supervision. Not much more work than doing the same job on my truck, I needed fewer tools for the Mooney, and Lycoming didn't use unique attachment methods on the back of the engine where its difficult to see (must be a Ford thing, my Chevy truck wasn't like that either).

Now my pretty yellow harness has one wire that's either red or blue, I forget.

P.S.--my new harness was Kelly brand.

Those yellow wires look nice. 

I didn't see anything obviously abraded in mine like that, my troubleshooting never seems to go that easily...lol.

[bcg]

It's a bad wire and Champion is forever backordered for them. We're trying to replace the wire but can't find the swaging kit.

Are there alternatives to Champion that are FAA-PMA approved? All I can find is a set for experimentals on Aircraft Spruce.

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[KSMooniac]

New Horizons Maggie Aircraft Ignition Systems - Maggie Ignition

BeechTalk - BT - WANTED - Review - New Horizons Maggie Ignition Harness

 

[bcg]

New Horizons Maggie Aircraft Ignition Systems - Maggie Ignition
BeechTalk - BT - WANTED - Review - New Horizons Maggie Ignition Harness
 

I sent them an email this morning, no response yet. When I called, I got voicemail.

Replacing the single wire solved the problem for now. I'll probably replace the harnesses anyway if I can get them, these look original to the plane. They're OLD.

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[hammdo]

New Horizons did mine a while back. I left a VM and it took them a day or so to get back. Product was excellent and worked perfectly with my SureFly.

- Don

[N201MKTurbo]

I have Maggie harnesses on my Mooney and Cessna. After the boys at the airport saw them two of them have them now. Cheaper and better than the competition. Better to support a mom and pop operation than the giant corporation.

[bcg]

I think this wire was probably a problem for some time. Flying after the repair was like a completely different plane. Much smoother, better climb and power, it just ran better.

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[carusoam]

Lots of good Maggie pireps around here…

They we’re good for selling half of a good harness for people that were replacing a single mag…,  Maggie half harness…

See if @HoJo87 is around…   

Best regards,

-a-