At 03:46 PM 7/28/2012, neil n wrote:
>For sure. I get it.    :)
>
>Maybe the nut on the stud can vibrate loose? Or other wires rub on
>stud end, get down to copper, "fzzzzap" ?

The usual trouble (not that it's usual) is for something out in the
engine bay to get shorted to ground.  That stud powers ECU, fuel
pump, injectors,* idle stab controller, O2 sensor heater, P/S
pressure switch.  Any of those wires or the B+ feed to the relay box
get shorted to ground and you let the magic smoke out, poof, starting
at the B+ lead through the relays all the way out to the
short.  Rare, but so are tetanus and rabies.  It was bloody
inconvenient when it happened to me, but I got an excellent used one
from Scott Daniel.  The Vanagon guardian angel allowed it to happen
half a mile from home, half a mile after a 700 mile trip and about
four days before a 1500 mile trip.

*The injector drive from the ECU actually grounds them; they're
always hot when ignition is on.

I haven't looked at what could happen actually inside the wiring
box.  If the B+ wire fell off the engine would stop, no big
deal.  Too tired to look at what else goes through there right
now.  Various sender leads and such.  The existing fuse in that box
is for the crankcase vent heater.

Yrs,
d