I got bus #2 home this week after an interesting problem that made for some slow going. The engine was dying every few moments as if the key was shut off, then, after about 10 minutes, it would start and run again. Rinse and repeat.
After a few cycles of this, I brushed against a wire while the engine was running again and it died instantly. I traced this to a small coil just atop the intake manifold. This coil screwed to a machined block between the braided line from the fuel filter and another steel line that T'd and ran to each bank of cylinders. I wasn't sure what the coil was until I pulled it off and found the following:
This is how the engine is controlled by the key switch. Removing power to the coil allows the metal disc to snap shut and block the fuel from flowing to the cylinders. Here's a simplified diagram: (It's no fun if I don't get to play with sketch-up at least once)
The component was located behind the turbo's output plenum and getting to it required removal of the alternator and the plenum.
Since this part is not available at the local autoshack and I needed to be 1100 miles in 48 hours, I decided to remove the disc, which would allow fuel to flow all the time. This, however, could be inconvenient when parking for the night and you don't want to wait for the 80 gallon tank to run dry. This was solved with a trip to the plumbing aisle of Lowes.
I took the right angle coupling attached to the input side of the fuel filter along with me and found a few brass fittings that allowed me to hook a 3/4" ball valve on the filter mount and can now shut down the engine by giving the handle a turn.
It's not as convenient as using the key, but it got the bus home and will work for moving it around the work lot until I can source the original part. If all else fails, I'll find an electric valve to put inline somewhere.
Anyway, hope this helps someone with a similar problem...