When I was a kid our old 1970's Volvo broke down and was left on the side of the highway. When the mechanic came, my grandad was turning the ignition to start it, the mechanic was putting his hand on a canister, about small water bottle size, on the firewall, in front of the steering wheel. I think he was seeing if it was over heating.

My head was just tall enough to be looking over the right fender at the engine. Then the canister blew-up, something went flying, I ducked, and the mechanic got soot in his eyes, thinking back it was pretty scary, and lucky for both of us. I was pretty much in the firing line, my memory does say it went over my head. Maybe not, but it must have been close.

So what blew up? was it a sealed/potted inductor ? Is there any big capacitor inside it that could explode ?? I'm guessing something overheated and or shorted and overheated, some gas pressure built up and blew the canister apart.

 

Personally never heard of a ignition coil blowing up!
But generally there would not be a capacitor internal, but probably oil filled?
Max.

 

I don't remember any liquid go flying, I can't say I remember any noise from it either, but there was for sure. I was probably 5-6yo

 

My guess would be that the canister was a can of ether. The mechanic would likely have been spraying it down the throat of the carburetor. This is a common technique used to get an engine started when it's starved for fuel. A mistimed spark or a reverse turning crankshaft might have allowed it to backfire up through the carburetor.

 

I don't remember any liquid go flying, I can't say I remember any noise from it either, but there was for sure. I was probably 5-6yo

Could have been Pitch (tar).
Max.