I was looking at 1992 sc400 coupe a day ago.
It was one of the barn car that spend last eight years sitting.
The problem was that turning the ignition key to ON causes something burning. The smoke was coming from the front part of the engine on the passenger side. The smell was awful and it smelled like burning electrical wires.
I turned ignition off and smoke was gone.
I immediately thought it was the alternator or starter. Maybe it got seized after so many years without moving.
What else could it be?

 

Also consider vegetation, spiderwebs, spiders, roaches and other organic material that may be getting cooked in this process.. I cooked a big *** spider on my exhaust manifold, I spotted it while replacing a power steering hose on a front wheel drive car. My friend who was helping me and arachnaphobic didn't see it, and I didn't say anything either until we were out, tbh I flinched so he kept asking and I kept deflecting about catching a rock in my back.. lol.

Also check grounds.