Ignition / Ignition coil problem

[TulsaFred]

The BE was running great with my rebuilt 1275. A couple days ago I relocated the coil from the generator mounting location to the body mounting location.
Went to start it today and it wouldn't start. Just cranked and cranked. Has gas but no spark.

Used my test light and there is current to the positive side of the coil when switched on, but no spark jumps across the plug wire when held close to the plug while cranking.

Touched the coil and it was extremely hot.

Did the coil go bad just from relocating it?
Other thoughts?

Fred

 

[Trevor Jessie]

Maybe the connection from the neg side of coil to distributor has a bad spot in it. Jumper it with a bit of fresh wire and see if anything changes.

 

[Gerard]

Could be a bad coil, but could also be a bad ground. Do you points or electronic ignition? Electronic ignition, Pertronix in particular, behave badly in this way of the distributor is not well grounded. Assuming your engine is freshly painted, you might not have a good ground between the distributor body and the engine block. I had this exact situation on an MG Magnette recently, with the same issue of a hot coil. Scraping some paint off the engine block where the distributor clamp bolts to the sleeve flange did the trick.

 

[dklawson]

The coil being extremely hot suggests that the current flow through the coil is continuous (the points are not opening). Though you did not mention doing anything with the points, check them anyway to make sure they have not closed up. If you have a Pertronix like Gerard suggested, the current flowing long enough to get the coil super hot may have also damaged the module.

That being said, moving the coil you probably disconnected and reconnected the coil low-tension wires. What ground is your car and what wires are on which coil terminals?

 

[TulsaFred]

Thanks guys. Electrical issues are really interesting problems to solve. As it happens, I fixed the problem without knowing for sure what fixed it. I moved the coil slightly in it's clamp, and I disconnected the high tension lead to test the coil with an ohmmeter. It tested, I believe, in proper working order (2.7 ohms on the primary, and around 10,500 ohms on the secondary).I left the low-tension wires in place while doing the testing with the coil in place as well. I just removed the high tension lead.
When I reconnected the high tension, and retested for voltage at the + side of coil (still there!), I figured I'd give it another try. Cranked and started right up!

So what was it?
The high tension wire not making good contact? But I had already removed and reconnected it at the outset and that didn't do it.
The moving of the coil in it's clamp? Not sure why that would do anything, unless it was somehow grounding the negative side, which did not appear to be the case.
Coil cooled down and become operative again? maybe

It helps to realize that a very hot coil implies continuous current running through it. That seems like it has to have been some type of negative side grounding issue. Maybe internal?

 

[Trevor Jessie]

I suggest carrying a spare coil for a while just in case.

 

[SD Bugeye]

I would pop open your dist. and look at the points see if maybe there was an arch and stuck together temporary.transfer of contact material a divit on one side and cone on the other
could be that the points were closed with ing. on for a long prod of time?
that would heat her up

 

[TulsaFred]

Took it for a test drive today, and when I pulled back in and lifted the bonnet, low and behold oil was dripping out of the coil! I think the oil is the insulator. Either the oil means the coil was bad and internally shorting, or the heat build up from some other issue caused the oil seal to fail.
I ordered another coil on amazon.com
Hopefully just a faulty coil.

 

[dklawson]

Oil is an insulator but it also there to conduct heat from the windings in the coil to the casing.

If you want a very reliable coil, in the future consider buying the Bosch Blue coil from Jeff at Advanced Distributors. There are "good" and "bad" Blue Coils. Jeff sells the ones from Brazil that have the better reputation.

 

[TulsaFred]

Thanks Doug, good advice. The epoxy construction of the Bosch coil would certainly avoid the issue I seem to be having.

 

[CaptRandy]

Had close to same problem and found that the plug wires were scorched and black carbon where the attached at the cap. Changed wires and cap and the problem went away. All I can figure is the "wire" core of the plug wires may have melted away and lost contact. Maybe Gerard can give some insight as to what could have happened.