PT 422 hard to start

MossRoad · Jul 3, 2017

Glad you got it running well again. :thumbsup:

BobRip · Jul 4, 2017

Thanks Moss. I have a new policy on ignition coils: If a non in use test shows it is bad replace it. If the same test shows it is good then find an in use test to see if it is really good. If you can't do that then replace it anyway. I had a chain saw coil fail last year and my test method showed it good. Maybe somebody out there has a really good way to test an ignition coil. I sure would like to find one.

ponytug · Jul 5, 2017

I just hook the spark plug lead up to a spark plug and ground it on the engine. If I get a big spark, I consider it good. What is your non-use test?

All the best,

Peter

BobRip · Jul 5, 2017

Tried that. It worked fine under that test. I am not sure what was wrong. Here is my theory. When it was running I reconnected the bad coil and then disconnected the good coil. It ran but you could see and hear it missing. Much more than running only on the good coil. Also the back fire through the carb occurred at cranking speed. Once is was running that went away. I suspect the coil was stuck on it's advanced timing. The electronics in the coil adjust the timing based on engine speed. If that failed it could be stuck on advanced timing. Hence firing too early and before the valves closed. A lot of guess work on my part. I could be wrong.

ponytug · Jul 6, 2017

I like your in use test. I hadn't thought about the coil having the timing advance circuitry in it. My shade tree test would never catch it.

All the best,

Peter

BobRip · Jul 6, 2017

Thanks. It would nice to confirm my theory, but the in use test certainly points to the solution.

MossRoad · Jul 8, 2017

I had a chainsaw coil go out last year as well. I got a good spark when testing, too. But after it started, I'd get crummy running and die. Took the coil out and found a cracked lead. Would have never seen it had I not disassembled it. It was the last thing left to be the problem after eliminating everything else.