Bad Coil?

[Warren Taylor]

Hey guys, got a 81 SC with the 3.0. Other day just acted like it had no spark, like the coil was intermittent, it would fire like every other fifth time and when it did it felt weak like it wasn't putting out enough power, I would have to take 5 min intervals to ensure a "good crank" until it eventually started. The coil has went bad before but not like this, (assuming it's the coil) it's only $35 but just didn't want to spend if that's not it. I took the wire out the coil and it arcs, I figured the coil got hot but I drove it the next day and same thing, once I get it running it's fine, but as soon as I turn it off and try to crank again it doesn't wanna start

[Steve@Rennsport]

Warren,

One simple way to tell if the coil is at the root of your hot staring problem is to carry a large can of electrical freeze spray. This stuff is used to rapidly cool overheated electrical components during troubleshooting.

Just blast the coil VERY thoroughly when this happens (remember, its a metal case and you need to get it cold enough to cool the core) to see if that changes things.

[Warren Taylor]

I felt the coil when all this was happening and it wasn't very warm, could the inside be though?

[HawgRyder]

The actual coil of wire inside the coil is potted (melted junk is poured in) to secure the whole assembly.
If the inside coil of wire gets hot in one spot...it can break and separate when hot (small hot spot) and when cool can join again.
Coils are either good or bad...bad ones do not miraculously "fix" themselves.
An MSD coil is cheap...works...and fits the holder...what more could you want?
Bob