DT466E will not shut down when key is off
Hello everyone. My bus, a 1999 Amtran/International 3900 with a DT466E engine, is having an intermittent problem shutting down.
The problem first occurred last year after a long and hot drive. All my running lights except headlights and brakes turned off while I was driving up a dirt road. When parked, I turned the key and the engine wouldn't shut down. I pulled the negative cable on the battery and the engine shut down then. I then replaced the ignition cylinder and the problem corrected itself.
Now, a year later and the problem is happening again. Replacing the ignition cylinder again did not fix the problem. This time, pulling the negative cable on the battery DOES NOT shut the engine down. I could only get the engine to shut down by pulling the harnesses off the ignition cylinder, not good I know. Further complicating the problem, once in a while the engine will shut down normally. Usually it's during the first startup after i've reconnected the ignition harnesses. I pulled the engine electronics fuse, not blown. But upon replacing the fuse, with the key in the off position, the bus's electonics came on, including my ABS light and some pumps, relays etc.
I'm thinking there may be a short somewhere backfeeding power to the fuel solenoid, but I'm not sure how this relates to the running lights and instrument panel lights not working.
I looked at the fuse panel, doesn't seem to be anything strange there. I am unsure where to find the "ignition relays," but there are two relays above the wheel well, below the fusebox, that I can't find diagrams for. May be one of those.
Any idea where I should start on this? Much thanks for any advice.