HELP - mag wires not right length!!!!

Webb · #1 05-18-2008, 06:32 PM

I spent the last hour reviewing mag wiring when it seemed the wires were not correctly cut to length (it came that way) My engine manual wiring is the same as the other threads I have read.

Mags from the back:
Left
42
13
Right
31
24

Here is the problem:

Left mag - the longest wire on it is on #4 and should be on #1. The shortest wire is on #2 and should be on #4.

Right mag - Longest wire on # 3 and should be on #2. The shortest wire is on #1 should be on on #3.

Lengths are perfect for the wrong cylinders!!!! If I could rotate each cap a quarter of a turn CCW, it would fix it. Problem I see is there are 3 screws and won't happen.

I thought about flipping the mags but it still won't do it. What's the best fix?

Webb
RV7A - N32WW

jsharkey · #2 05-18-2008, 06:54 PM

Quote:

Originally Posted by Webb

I spent the last hour reviewing mag wiring when it seemed the wires were not correctly cut to length (it came that way) My engine manual wiring is the same as the other threads I have read.

Mags from the back:
Left
42
13
Right
31
24

Here is the problem:

Left mag - the longest wire on it is on #4 and should be on #1. The shortest wire is on #2 and should be on #4.

Right mag - Longest wire on # 3 and should be on #2. The shortest wire is on #1 should be on on #3.

Lengths are perfect for the wrong cylinders!!!! If I could rotate each cap a quarter of a turn CCW, it would fix it. Problem I see is there are 3 screws and won't happen.

I thought about flipping the mags but it still won't do it. What's the best fix?

Webb
RV7A - N32WW

There seem to be a few of us working with ignition harnesses this weekend. What make and model of mag are you using? Mine isn't like the manual.

Check out these threads

http://www.vansairforce.com/communit...ad.php?t=17320
http://www.vansairforce.com/communit...ad.php?t=30138

Jim Sharkey
RV6 - Wiring

Radomir · #3 05-18-2008, 07:30 PM

It's important to match the cylinder numbers, but it's NOT important whether it's top vs. bottom plug... that thing (as shown on the drawing) is a convention, not a requirement. It's absolutely irrelevant whether left mag fires top plug on #1 or bottom plug on #1.. and so forth.

So, if you can "make it work" then you can do so.. ignore those drawings.. just match numbers.

Webb · #4 05-18-2008, 07:48 PM

Jim,

I just went out to the shop with a flashlight and checked the spark plug nuts. The are marked and the lengths are proper for the markings but how they are connected to the mags doesn't agree with my Superior manual or the Lycoming diagrams on the threads you provided. I checked those threads earlier and they are the same ones I looked at before making this post. When I said if I could turn them each a quarter turn, they would match my manual and the other manuals in the threads.

Book for left mag and threads
4 2
1 3

My left wiring
1 4
3 2

Book for right mag and threads
3 1
2 4

My right wiring
2 3
4 1

I kid you not, if I could turn each a quarter of a turn, they would be perfect. My gut is the spark plug leads were not wired correctly. I'm calling Eagle Engines who built the engine unless there is an easy way to pull the caps, and rewire. My gut also tells me this shouldn't be that hard since plug wires do go bad and have to be replaced. However, not having done that before - its just a guess.

So I guess my request for help is how big a deal is it to rewire the spark plug leads??????

Webb

az_gila · #5 05-18-2008, 07:55 PM

Quote:

Originally Posted by Radomir

It's important to match the cylinder numbers, but it's NOT important whether it's top vs. bottom plug... that thing (as shown on the drawing) is a convention, not a requirement. It's absolutely irrelevant whether left mag fires top plug on #1 or bottom plug on #1.. and so forth.

So, if you can "make it work" then you can do so.. ignore those drawings.. just match numbers.

Well not quite....

The "convention" is in place to enable the correct application of spark plug rotation. The pulses are both negative and positive, and the recommended sequence of spark plug rotation, along with the correct convention of wiring, evens out and extends spark plug life.

Of course, if you don't bother to rotate your spark plugs, then ignore the wiring convention.... YMMV

gil A

Webb · #6 05-18-2008, 08:23 PM

After reading Jim's post, I realized that we both had the same issue. Too much of a coincidence.

I went out to the shop and got the flashlight and mirror out. The Unison slick mag cap has cylinder #1 stamped top right (left mag) instead of bottom right. Same for right mag. Darn thing is rotated 90 degrees from the drawing.
Bet your bottom dollar I'll make the corrrection in my manual although I doubt I'll forget this one.

This makes the wires correct and correct length for the cylinders.

Mystery solved, cased closed. I don't recall who posted the info on Jim's post about the cyclinder # stamp on the plastic cap - but thank you.

Webb

jsharkey · #7 05-19-2008, 04:38 AM

Quote:

Originally Posted by Webb

After reading Jim's post, I realized that we both had the same issue. Too much of a coincidence.

I went out to the shop and got the flashlight and mirror out. The Unison slick mag cap has cylinder #1 stamped top right (left mag) instead of bottom right. Same for right mag. Darn thing is rotated 90 degrees from the drawing.
Bet your bottom dollar I'll make the corrrection in my manual although I doubt I'll forget this one.

This makes the wires correct and correct length for the cylinders.

Mystery solved, cased closed. I don't recall who posted the info on Jim's post about the cyclinder # stamp on the plastic cap - but thank you.

Webb

The beauty of VAF - and 5,000+ RVs to get experience from

Lots of people at the same stage
Jim Sharkey

Webb · #8 05-19-2008, 06:23 AM

Quote:

Originally Posted by jsharkey

The beauty of VAF - and 5,000+ RVs to get experience from

Lots of people at the same stage
Jim Sharkey

I'm glad I spent the time verifying - I just hated losing 2 hours of time in which I would have had the wires routed and secured.

Thanks for your help - hope I helped you.

Webb

Pirkka · #9 05-19-2008, 02:01 PM

Quote:

Originally Posted by az_gila

Of course, if you don't bother to rotate your spark plugs, then ignore the wiring convention.... YMMV

But in a long run, does this really matter? I read about rotating plugs earlier but can't remember all details (added it to the subscribed threads for future use). I assume in a long run, the ninth time the plug should be at the place where it started it's rotation and while that it has been in every spark plug hole by then. If so, it should be as much in lower and upper holes as well as get same amount of negative and positive pulses.

I might have said that shorter, but hopefully you got what I meant.

az_gila · #10 05-19-2008, 04:05 PM

Quote:

Originally Posted by Pirkka

But in a long run, does this really matter? I read about rotating plugs earlier but can't remember all details (added it to the subscribed threads for future use). I assume in a long run, the ninth time the plug should be at the place where it started it's rotation and while that it has been in every spark plug hole by then. If so, it should be as much in lower and upper holes as well as get same amount of negative and positive pulses.

I might have said that shorter, but hopefully you got what I meant.

Pirkka,

Your statement would be true if it was a true rotation, with a specific plug passing along all of the holes.

...but it's not a true rotation... the Continental 6 cyl. pattern can be seen here...

http://www.sacskyranch.com/spark.htm

It's more like a swap between pairs of holes. If this pattern is followed, then a single plug might always get positive (or negative) pulses for it's whole life - if the wiring convention is not followed.

gil A