Is the front cover secure ?
Have you had the front cover off of the engine, the one that is held on by two allen head bolts ?
There is a roll pin at the bottom where the cover goes, it's called an anti-rattle pin .
Just a thought .
If you do decide to remove the cover, remove the positive cable from the battery, there are 'hot' terminals on the diode board, they are directly connected to the battery, so they have power to them all the time regardless of the key position in the ignition switch .
If you touch the cover to one of them with power available, you can damage the diode board .