I have a 1968 chevy 6 cyl. in one of my vintage cars and it suddenly stopped, of course at a 4 way stop. Anyways after pushing it out of the intersection, I determined that it was a spark issue, and not fuel. I finally got the car going and made it home ok. Shut it off and it fired right up again. I'm thinking that it was poor contact perhaps. I cleaned up the terminal ends with some sandpaper I had in my tool box, on both small wires at the coil, even though they were tight and the ends looked fine. When I pulled out the coil wire the metal clip on the end of the wire that makes contact between the wire and the coil stayed in the coil. So I thought that might be the issue. I got it out with needlenose plyers, and recrimped it back on to the coil wire. When I looked into the end of the coil, I noticed a post sticking up with a slot on the end of it. The post was very rusty. I tried to scratch the end of it with a small screwdriver, to get fresh metal. ( difficult to get down in there). Then I held the end of the coil wire to the top of that post where I had scratched and still no spark. But after playing around with it for some time, finally I got spark and headed home. While on the side of the road, I took a voltage check with a 12 V tester on both + & - sides of the coil. Bright light on the positive side, dim light on the - side. But after cleaning those wire ends, I had a bright light on the - side. So perhaps that was the issue. But they were both tight and I've put about 3 thousand miles on it without any issues. So my question is what's with that post? When I put a screwdriver in the slot on that post, it was tight, and I could unscrew it. However not knowing what would happen if I kept unscrewing, I decided not to go there before I knew more. Can I simply unscrew it and clean it up and screw it back in? At this point I'm****uming that my coil is ok, right? The other curious thing is that there is a condenser attached to the positive side of the coil. I have read that that might be for radio noise suppression. Is that correct?
There have been condenser/capacitors for years on coils, regulators and generators in the past, but not lately. Most were for radio static.
Seems there should be a brass cup(?) held in with that screw. The female, cup, makes good contact with the male fitting that you crimped back onto the coil wire.
Thanks for that picture, and yes that's what I'm used to seeing when I look in there. However I think we have two different animals here. That centre post on mine sticks up about at least a half inch. The outside diameter is about the same as the inside diameter of the cylindrical metal piece that attaches to the coil wire. So basically it snaps into place over that post.
The metal contact on the wire is supposed to fit into a metal tube in the coil. I don't know if that's what was causing it to not run, but might want to investigate getting another coil, since it's easy for you to spend money replacing parts. Since it's not my money
I'm not suggesting you buy this, it seems overpriced, but the photo looks much like what I posted above: https://www.classicindustries.com/product/1968/chevrolet/all-models/parts/k6024.html
I have ordered another coil which will arrive by noon tomorrow. However I'm not convinced it is the coil that failed. I'm leaning towards a bad contact on that male post that protrudes out of the coil. ( as opposed to the common female cup ) I pulled the coil wire off the distributor, pulled back the boot and placed it about a 1/4" from the block. Then I made sure the points were closed. Turned on the ignition and then separated the points. I got a strong bright spark from the end of that coil wire. So I'm thinking the coil is ok. I have an external ballast resistor and I also checked it with a multi meter and it seems fine. Nothing wrong with packing a spare coil. But I would like to know why it suddenly quit. I'm thinking it was just poor contact ( corrosion) on that centre protruding post. Once the new coil arrives I'll definitely have a look at the coil and unscrew that centre post to have a better look at it. I keep thinking if I do it now, once that centre post is unscrewed, there will be a spring and a ball under that post and they will shoot in different directions across the shop never to be seen again. Once I get the new coil, the post will simply unscrew without any issues. Murphy's law.
I doubt that's what was causing the problem. But it's difficult to troubleshoot it when it's running...much easier when it's not running.
The re-crimped high voltage coil wire probably won't last too long, it would be best to replace it or carry a spare.
There are two different coil wire connectors inside the coil. One has a stud that is like the end of the spark plugs and the terminal in the coli wire snaps over the top of it like the plug ends do. The other has the outside brass ring and the coil wire terminal has little nubs that snap inside of that brass ring. You need the correct connector on the coil wire that matches which ever terminal is in your coil. They are not suppose to be interchangeable, but I have seen many cases where the incorrect terminal ends were forced together. That almost always kills the terminal on the coil wire, but I have also seen it damage the coil terminal as well. If either the coil terminal, or the coil wire terminal (or both) are damaged, the damaged coil, or the damaged coil wire (or both) needs to be replaced. I've seen the terminal on the wire replaced, but it often doesn't last very long. I've not ever seen the terminal in the coil replaced and have it work correctly, it nearly always causes an oil leak from the coil and the loss of the oil in the coil is a death bell for the coil.
Here is a typical GM late 60's (points style ignition) coil wire. The end with the larger cap goes on the coil. The male connector fits tightly in the female insert inside the coil, that was pictured earlier. The smaller cap goes in center of distributor cap. Second photo shows the male connectors a little better with the caps out of the way.
No need to disassemble the new coil. Just use a coil wire with the proper male connector. It sounds like your current coil wire has a plug wire type terminal that used to come with 'make your own wire set' which simply bends over the end of the wire. Can you provide a photo of your coil wire?
I hit the wrong*****on too quick. If you check a coil with the points closed, the ignition side of the coil will have something less than battery voltage and the distributor side of the coil should have no voltage. If the points are open you will have battery voltage at both terminals. When you got a dim light on the distributor side my guess would be the points were closed but not making good contact or the distributor was poorly grounded. That was probably your real problem. As for having a bad connection at the coil secondary (center post) realize that with a good set of points and condenser, you can make over 20, 000 volts. It will jump most bad connections where the wire connects. However, if the coil wire is open, that would be a problem. A badly corroded connection on the high tension coil wire points to an open or almost open coil high tension wire. Many years ago I was trying to make an open coil wire as a bug for a troubleshooting exercise (I taught school). The car was a 70's Plymouth and it had orange coil and spark plug wires. I found some vacuum line that was the same color and made up a "phony" coil wire. I installed it, hit the starter and the engine started right up. However, if you got too close to the coil wire it would shock the***x out of you. It seems that the vacuum line I used had a high carbon content.
Sounds like you are headed in the right direction. Please report back here in a week or two how your repair came out.
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