Our garage door opener stopped working the other day. When it was lifting it would hesitate and then the unit started smoking! As soon as I unplugged it, the smoke stopped. I noticed that the member that's attached to the garage header was loose and twisted. After I tightened up the lag bolts and tried the opener again, the motor worked but it would hesitate and start to smoke again and then stop when I unplugged the unit. After an easy cover removal, and another exercise of turning on the opener, the white smoke was clearly coming out of this round device that was held by a simple collar. No real fire danger as I would not let it smoke for more than a second or two. So, it was not the motor burning up or any wiring burning..........it was the: Motor Starting Capacitor! The motor starting capacitor is a tubular thing with four wires connected with spade plugs. I ordered one online, got it in three days, plugged it in and it worked! I almost, (frivolous me) bought a new opener, which would have fixed the problem, as well. The capacitor was $18.00. Door opener $200. Apparently, motors that have to start under a heavy load, like a garage door, need these capacitors. My door was operating under an extra heavy load because of the twisted and loose structural member tied to the door header.
Consequently it burned up the capacitor before it would make the motor do it. I'd forgotten what a pain it was to lift my own garage door and the pain was in my back.