Perhaps I'm a little foggy on my high school physics, but as the ignition system gets its power from the "+" side of the battery, then for that circuit to "go somewhere", the power going through the ignition system ends up at the spark plug ground, which is the engine block . . . and what connects it to the "-" post of the battery? Isn't the "fusible link" an inline fuse for the starter circuit only?
If the fusible link "arced", what did it arc to and why?
The ground for the ign control module does need a good case ground to the chassis/body.
I agree that when a "ground" is lost, then electrons seek out the nearest place to jump "to ground", which can cause some "interesting" situations.
CBODY67