Mag Troubles Take 2

[GAHorn]

If ignition troubles are affected by temperature .... it' s been my experience that the coil is faulty. Many times a cold coil will run just fine ...but when hot will fail integrity due to expansion.

[W.J.Langholz]

Good Golly George...grab a couple mags, jump in the ol air o plane, fly up there and get this guys palne running already!!!!

[GAHorn]

Good Golly George...grab a couple mags, jump in the ol air o plane, fly up there and get this guys palne running already!!!!

YOU buy the gas! HE buy the beer! and Ol'Gar and I'll be there. (Gar says He thinks it's the spinner and said he'll take if off his hands for FREE!.)

[W.J.Langholz]

Good Golly George...grab a couple mags, jump in the ol air o plane, fly up there and get this guys palne running already!!!!

YOU buy the gas! HE buy the beer! and Ol'Gar and I'll be there. (Gar says He thinks it's the spinner and said he'll take if off his hands for FREE!.)

Why doesn't Gar use the spinner he had on top of his head sitting out in the rain??!!!!????

[W.J.Langholz]

this thread does have a special interest to me. This spring when I purchased my plane in St louis I had a mag go bad about 45 mins out on my return trip with the plane I had just spent my hard earned money on. We had climbed to about 8500' and just had leveled out when we heard what sounded like a bumping noise, almost like something was loose outside. It wasn't constant but on and off every 2-3 minutes. I thought first maybe it could be carb ice so I put the carb heat on, it stopped for awhile and then came back. I leaned out the mixture which I thought helped for awhile but then came back again, at this point we decided to look for the nearest airport to put it back down on the ground. Being that it had been 20+ years since I had done any flying, I turned the plane over to my good freind and CFI co-pilot to get it down fast and safe. When we landed and taxied over to the hangar we switch the mags and on the left one the planed died. The next day we took both mags off and went over to a excellent shop and they both bench tested o.k. we picked up a new switch and harness went back and installed the original mags new switch and harness. Ran up the plane and had the same problem. In the mean time I had contacted the guy I had purchased the airplane from and told him we didn't make it very far and the problem we had incountered. He is one of the rare people that you come accross once in a while, he sent his own mechanic with 2 band new mags down had them installed not only paid for them but for the new harness and switch. Need less to say the plane ran great and still does. I called him several days later and asked if he had fond out anything on the mags, he said they bench tested them again and on the bench they both indicated they were fine but we know different so they were going to rebuild them both.
I feel very hornored to have met such and individual, and I can relate to this problem first hand. It can be very frustrating to say the least when you think you have looked at everything and the darn thing still don't run.

Hope you guys figure out what's wrong and get it going. I'll be waiting to see the out come.

[rupertjl]

So the good news is that I flew for an hour today. I checked the harness for proper placement, checked the cables with the test just because I had them off the plugs, then I decided to put the new plugs in. Ran it up and everything checked good to my amazement. I let the oil temp come up a bit and then checked full throttle static RPM and it was reading 2200. Did another mag check and still good, 50-75 RPM drop. Put it back in the barn and finished installing my Dip Davis latches, put the cowling on and flew it for an hour. Came back and did another mag check, everything looked normal. Sounded fine in the air and guages al read normal.

SO now my question is what about the spark plugs that I previously had in make it run like that during mag checks? When I swapped plugs top to bottom, why didn't it exhibit the same problem on the other mag? Why did the bench check on the plugs check out fine? I'm skeptical that the new plugs fixed the problem but the engine checked fine both pre and post flight so I have no other reason not to think so.

Whatcha all think?

At least it was good to finally get up in the air, even if it was to circle the airport at 2500' just in case

[GAHorn]

Only a possible explanation: Cracked insulator. Maybe one had been dropped at one time? (One mag.... the one just overhauled.... may put out hotter spark allowing it to short out across the fracture..... Older mag just didn't jump all the way thru the crack.) (This is a WAG.)

[jrenwick]

I'd be tempted to put the old plugs back in to see if the problem returns....

[N1277D]

Or you could put the plugs for sale on e-bay

[Bruce Fenstermacher]

As George pointed out who knows why switching plugs top to bottom didn't bring this out to include are you absolutely sure you switched all of them of could some of them have been returned to were they where originally.

Because I could never bring myself to get rid of all 12 used plugs I would have to put the old plugs back in to find the bad one that's bad and get rid of just that one.

Then the eleven left would can join the pile of good 170 stuff your accumulating with the old harness and ignition switch.

[Roesbery]

Another idea to consider is if someone sometime did some drawing with a lead pencil ( Graphite ). Some people have been known to do things like that as a joke, and sometimes it is unintended, but can cause lots of head scratching.

[rupertjl]

I still have the old ones and I will keep them, clean them, inspect them a little better. Next time I have the lower cowl off I think I will swap them back in to see if that's what happens...

just for more info-I put these plugs in about 3 years ago and they have roughly 300 hours on them, I've never dropped them and have cleaned and rotated each year at annual. They were Champion plugs, i swapped Autolites in the this time...due to price mostly...if I would have started with plugs first I probably went with Champions again.

I just want to put a few hours on it now...I missed some of the best flying weather the past two months!

[GAHorn]

Both Champions and Autolites are good plugs. I like the Autolites over the Champions for only one reason: They have a higher nickel content in their shells, and therefore do not rust as quickly externally. Otherwise there is no performance difference.

[Showboatsix]

I replace mine every 2 years, at a total of $200.00, it is not worth my time or safety to regap them, damn cheap insurance I say, and no I do not Ebay them, they are tossed out. I use the Autolite brand.

Dean

[W.J.Langholz]

I still have the old ones and I will keep them, clean them, inspect them a little better. Next time I have the lower cowl off I think I will swap them back in to see if that's what happens...

just for more info-I put these plugs in about 3 years ago and they have roughly 300 hours on them, I've never dropped them and have cleaned and rotated each year at annual. They were Champion plugs, i swapped Autolites in the this time...due to price mostly...if I would have started with plugs first I probably went with Champions again.

I just want to put a few hours on it now...I missed some of the best flying weather the past two months!

Been gone for a few days...just got back, good to hear you are flying again