Spark jumping on the surface of the coil assembly?

[Dante04SRT]

I was doing a compression test tonight and I disconnected the coil from the dist before doing the test, but saw something I wasn't expecting. There was a spark jumping from the one of the terminals on the coil to the center of the coil, where the spark plug boot attaches.

Attached is a pic. Is this normal? Its been so long since I've worked on a motor with a distributor, I can't remember, but don't think so.

 

[Don S]

Re: Spark jumping on the surface of the coil assembly?

The coil tower is probably cracked. Usually caused by a bad wire or plug that won't fire. I'd recommend replacing the coil and the wires.

 

[PhilDx]

Re: Spark jumping on the surface of the coil assembly?

I would say it's not normal. I know if it happens on a distributor cap it's time to replace it. The insulation breaks down and hairline cracks allow the current to jump to the nearest earth or 'leak'.

 

[Robj]

Re: Spark jumping on the surface of the coil assembly?

When you did your compression test, you should have grounded the high tension wire going to the distributor. You probably did not, and the current was looking for the easiest way to ground, which was through the boot and onto the coil ground. This is normal based on what happened, but it also may indicate that the insulation on your wires is breaking down. Maybe time for a new wire set.

Have a great day,

Rob.

 

[Dante04SRT]

Re: Spark jumping on the surface of the coil assembly?

When you did your compression test, you should have grounded the high tension wire going to the distributor. You probably did not, and the current was looking for the easiest way to ground, which was through the boot and onto the coil ground. This is normal based on what happened, but it also may indicate that the insulation on your wires is breaking down. Maybe time for a new wire set.

Have a great day,

Rob.

Thanks for the input; The wire set is brand new, so I'm thinking it was a grounding issue.

 

[Robj]

Re: Spark jumping on the surface of the coil assembly?

I would also do as Don suggested and check the coil tower for cracks. If it is OK, then I would not worry about it.

Have a great day,

Rob.