Arcing across coil terminals

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smokinnjokin

smokinnjokin

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Car didn't want to idle right today, popped hood and noticed a loud clicking sound.

The ignition coil positive and negative leads are (both alternating) arcing with the distributor lead. The connections are all firmly attached, clean new hardware, and the distributor wire is firmly seated in with a dust boot. What gives? Why is the ignition arcing all the sudden?

Standard points on a 360. Ballast resistor installed, Standard UC12x coil with a factory distributor.
 
I’ve had that happen on my truck when I was young, broke, and dumber.

In that case, the wires were old and dry rotted. I knew they were old and cracked BUT it still ran. It’s almost like the electricity was taking the path of least resistance.

I would replace the plugs with the proper gap and replace the cap, rotor, and wires.
 
Fresh plugs, .035" gap. New wires. Just cleaned the cap contacts. There is discoloration all over the coil boot though, looks like burn marks from the arcing. The car ran like a top right after the new plugs and cleaning the cap. This problem just developed after a couple days of running great. Daytime temps are in the high 90's though, not sure if that is related. The coil and distributor are getting very hot, especially after shutdown when water stops circulating.
 
smokinnjokin said:
Car didn't want to idle right today, popped hood and noticed a loud clicking sound.

The ignition coil positive and negative leads are (both alternating) arcing with the distributor lead. The connections are all firmly attached, clean new hardware, and the distributor wire is firmly seated in with a dust boot. What gives? Why is the ignition arcing all the sudden?

Standard points on a 360. Ballast resistor installed, Standard UC12x coil with a factory distributor.
Click to expand...
It's got a carbon track, replace the coil
 
You may have a high voltage (secondary) problem, check the coil wire that it's not open, and check your plug wires and plugs that one is not cracked, open.

If that is not the case, the coil is likely carbon tracked or cracked as mentioned.
 
Look to your plug wires! ^^^^. If you run a pertronix etc, are you using good old fashioned solid conductor wires? You should not without knowing!

I switched from Mopar Electronic to Pertronix and thought I knew better, I was wrong and one issue was just as you describe! Never mind all the other scatter. Live and learn!
 
Ok so I don't see any cracks in the tower or carbon tracking, my plug wires are 8mm "low ohm suppression" wires, only a few months old. My prime suspect is my cap. The brass terminals (they are brass colored anyway) have already got carbon markings on them after i just cleaned them to bare metal the other day.

Does anyone know a part # for a high quality, copper-terminal cap? Preferably the ones with the extra-wide terminals? I know the original oem ones cost a fortune, is there a decent quality reproduction out there?
 
smokinnjokin said:
Ok so I don't see any cracks in the tower or carbon tracking, my plug wires are 8mm "low ohm suppression" wires, only a few months old. My prime suspect is my cap. The brass terminals (they are brass colored anyway) have already got carbon markings on them after i just cleaned them to bare metal the other day.

Does anyone know a part # for a high quality, copper-terminal cap? Preferably the ones with the extra-wide terminals? I know the original oem ones cost a fortune, is there a decent quality reproduction out there?
Click to expand...

can you take a picture of the inside of your distributor cap so we can see what the terminals look like in the burn pattern on them.tia
Sometimes it's a good idea to loosen and re tighten the bolts on the box to establish greater contact area lost from oxidation.
 
AEC90A62-7F93-424D-B4B3-AECF998BB277.jpeg
FE406046-784C-4A0B-923F-BF40B2D29D16.jpeg

Points, not electronic ign.
 
smokinnjokin said:
Ok so I don't see any cracks in the tower or carbon tracking, my plug wires are 8mm "low ohm suppression" wires, only a few months old. My prime suspect is my cap. The brass terminals (they are brass colored anyway) have already got carbon markings on them after i just cleaned them to bare metal the other day.

Does anyone know a part # for a high quality, copper-terminal cap? Preferably the ones with the extra-wide terminals? I know the original oem ones cost a fortune, is there a decent quality reproduction out there?
Click to expand...
@halifaxhops has quality caps
 
Almost looks like the coil wire is arcing at the coil. See the discoloration?
 
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The arcing is between coil terminals and primary wire under the black boot to the coil tower. Have not observed any arcing between coil and distributor.
 
I'm going to repeat in a diferent way what I said earlier. There are only so many things that cause a coil to arc. OPENS in the secondary circuit. This includes bad rotor phasing, which leaves a big gap in the path from coil to plug, a bad coil wire or bad plug wire, or something wrong with a plug, such as internal break in the resistor, missing electrode, cracked, might even happen with weak coil/ boot insulation if you have a lean cylinder

WHAT IS THE common with all of the above? RISING SECONDARY VOLTAGE caused by an open. When properly connected, the spark voltage only gets "so high." If you disconnect a plug wire, example, that point is just like lightning, "looking" for a place to strike.

The second cause would be an insulation crack or chemicals on the coil, etc encouraging it to arc across at that point.
 
A new cap is not going to change anything.
 
halifaxhops said:
It has to be the coil has a hair line crack for sure.
Click to expand...

Could well be, but I'll be damned if I'd crammed that coil up close to the distributor like that. How the heck can he grab the vacuum can to make timing adjustments? Why do things to make stuff harder than it already is? That coil needs to be moved for a pile of reasons. Look at the dark traces on the coil wire where it goes into the boot. It's been arcing there. That's carbon trace.

To the OP, have you raised the hood with it running in the dark yet? That's one of those old fart tricks, but it works really well.
 
Yup way to close. I wonder if it is possibly going to the distrib housing when it is humid????
 
That's also a electronic ignition coil also in the summit catalogue. The standard shows both? Wonder what the recommended mounting position is also vertical or horizontal?
 
Do this test and if it is good I would change the coil wire at least the boot on it.
testcoil1.jpg
testcoil2.jpg
This testing procedure is valid for just about any automotive coil. Using an ohmmeter, check the resistance between the side terminals of the coil. Do this with all of the wires to the coil disconnected. You should see 0.75 to 0.81 ohm of resistance. Then check the resistance between either side terminal and the center high tension terminal. The reading should be 10,000 to 11,000 ohms. Any significant deviation from these numbers would indicate that the coil is defective.
 
Here's what I think is happenin. I think it's arcing from the plug wire on the cap, to the coil wire through the boot and to "whatever" it is grounding on at the coil. Me and Kirk were workin on his Chevelle one day after school. We were adjustin the valves. Hot little 307 Chevy......we had everybody snowed it was a 350 cause it ran so good. lol Anyway I had removed the coil wire. On the factory coil mount on those late 60s (his was a 69) and early 70s point type Chevys, the coil was mounted right next to the distributor, pretty much vertical with the coil tower only about 4" away from the coil nipple on the cap. I had the coil wire removed so it wouldn't start. Ha! I told Kirk to bump it to get the cam on the base circle, and BAM it busted right off with the coil wire sittin on the cowl under the the wiper blade. So don't think for one minute that the spark cannot travel a great distance if all the conditions are right. We found out the hard way!
 
Not much info on that coil either even in the standard site says it fits everything. If it is oil filled it should go vertical to cover all the windings.
 
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