Chasing sparks . . .

[Spanky]

My young neighbor’s dad came over to look at my T–bucket, and asked if I would start it up so he could hear it run. No problem! Vroom-vroom! He liked it. After I shut it off he said he noticed a spark jumping from the number 2 cylinder plug boot along the outside of the plug. I checked the boot, and it was tight, and the wire seemed good so I just blew it off as a happenstance. The next morning, by the light of day, I reexamined the plug and wire, and pulled the boot off. Then I noticed it: big crack in the ceramic insulator! I just changed plugs about three weeks before, and don’t know if I cracked it then or what. It’s been running fine. So, my advice: run your motor in a dark environment once in awhile and look for errant spark travel. Might save you a headache later.

 

[Kevinrevin]

I remember back in high school ('81-ish) a buddy gave me an Accel SuperCoil for my '71 Javelin. The spark-show before I got new plug wires was incredible.

 

[fletcherson]

I had a similar issue on a truck recently only it had a dead miss. Thought it to be wiped cam or valve related because the plugs, wires, etc were all replaced by me not long ago. Turned out to be a cracked insulator... no clue how it happened. Glad that’s all it was! FYI, I have seen plug wire boots leak and arc to the plug body. Ignition grease is our friend.

 

[Guy]

Same thing happened to me but it was the distributor cap was arcing from one of the screws to the base plate must have been a crack in the cap

 

[fletcherson]

Same thing happened to me but it was the distributor cap was arcing from one of the screws to the base plate must have been a crack in the cap

rotors will do that too, they get a hole burnt in them and short to the distributor shaft. Can be a real head scratcher when diagnosing because the hole is usually small and hard to see and being inside the cap hides the arc.

 

[rubicon]

I remember my dads car running real ruff. We put a blanket over it and could see the arcing along all the wires. everything under the hood was damp. Wiped it all off and it started running like new. cheap wires back then.