how do you people test ignition coils??

[J.W Younger]

I do it like I do with 9 volt batteries, I stick the spark plug against my tongue and pull it over. If I get shocked, it's working, no shock time to replace the coil.

better still get the neighbor from hell to put his tongue on it while you pull and watch.
I realize not all of you have a neighbor from hell so I'll be glad to loan you mine.

 

[WildnCrazyGuy]

Bump...

Curious about an issue I'm having and a coil SEEMS to fix it. I got a well used BR600 and it finally seems to run right, but after some time, out of nowhere, it acts up. Tried a new plug, adjusting the valves, etc. It just cuts out like it's losing power at full trottle, but will usually idle fine when doing so. Full throttle, acts like it has no power. So...

I bought me a used BR600 coil off ebay, put it on and so far, knocking on wood, it has not even sputtered. Full power all day long. I think I've run it about 4-5 hours so far, no problems. Just for the kick of it, I put the old coil back on today and ran it. It ran fine for about the first tank of gas, then the second, it started sputtering, and even shut off on me at WOT. So, I swapped the coil back to the new (used) one and it ran about 3 more tanks without issue today.

My question is what might make a coil going bad do like that, or have I just not run it enough yet? My limited experience has been either the coil works, or not. When it gets hot, why would it stop working, or in my case, intermittently and only seems to be WOT, idle seems ok? Just after it cut off on me today and before I swapped back, I pulled the crank and it started right back up maybe 30 seconds after it cut off and was full power, sputtered again, then full power, then I said heck with this, I put the other coil back on and like I said, it ran fine the rest of the day.

Other question is like OP asked, with my situation, I'm getting spark, but it acts up while it's hot, how to test a coil in that situation, test meter tell me anything when cold? So many questions to ask, but I don't know the right questions to ask.

 

[heimannm]

Steve, when things get hot, they expand. If there is a fault in a wire some where, it may open when the whole body of the coil heats up. Same thing with coils with built in electronics, may be O.K. cold and fail when they heat up the electronics may quit working properly.

I haven't checked it precisely but the book says the coil on my 066 Stihl won't fire if turning less than 600 RPM to avoid issues when starting the saw. I can tell you that pulling it over slowly (with the plug out) produces no spark, pull it quickly and you have a nice, fat, blue, snapping spark.

Mark

 

[WildnCrazyGuy]

Thanks Mark. I'll keep the ebay coil on it and run it assuming the original is just bad. Hopefully that fixed my problem. Time will tell if it's another issue. But for now at least, it seems to purrrrrrr.