[elonblock]

Also make sure that the holes where the fastener attaches to the sheet metal are bare metal and have a good bite. And doesn't have a thin coating of paint insulating the grounding fastener.

This is critical especially if the car was touched up or restored in the engine bay with fresh paint.

It only takes a thin coating to insulate the fastener and seek a ground elsewhere as was mentioned previously.

I ended up welding up the holes in the firewall and redrilling, because the holes were oversized and the screws were basically a slip fit.

It can be a real hair puller!