My neighbor's 7.3 just went away on a flatbed yesterday. He made it to the front of my house when it started running real rough - sounded like it was running on 5 or 6 cylinders. He thought he was out of fuel, so I drove him to grab some diesel, we dumped it in, and it was still running rough ..... then I could hear cylinders dropping one by one, until it stalled and would not start. I took that strange round cap for the fuel filter off, and poured some diesel in there, tightened it back up, cycled the key a bunch of times, then cranked ... and cranked .... and cranked! Was only getting a very sharp knock on one cylinder. Pulled that lever & let the diesel pee out, refilled, and tried again. Long story short, it went away on the flatbed.
Probably something electronic, no doubt.