[77newell]

I'm guessing the key being on is needed to energize the engine ecu and run the injectors. The rear start may only energize the starter circuit and bypass the neutral switch of the transmission. If the engine turns over with the rear switch but not the key switch then there is an open somewhere in the circuit through the neutral switch. I had this happen on the 77 coach and it was a wiring connection and not the neutral switch itself but each case is unique.

It would be interesting to know for certain that the rear switch does not energize the engine ecu. If it doesn't, you could turn the engine over but it would not start.