I just bought a 1993 Ford F250 with a 7.3 Non turbo, the guy I got it from said it sat for a while, and they drained the fuel tanks, and got quite a bit of water out of them, and they put new fuel in it, and it ran good, then, the fuel pump was acting up, and he had a friend put a new one on ( A Thermoking electric pump) there is a toggle for the fuel pump, and a toggle for the WTS light, it just started running rough on him one day, and he never had it checked out to see why. What it is doing, is this: It will randomly misfire at idle, and when it does, it throws a puff of black smoke, only when it misfires, if I raise the RPM's above 2000 or so, it clears up, and quits the random misfires, and no black smoke. When I drove it, it spewed excessive black smoke, I mean A LOT of black smoke! The truck is extremely nice, and looks like it was really well taken care of, it has some new injector lines also. I had a helluva time getting it started today too. I suspected air in the injection lines, so I cracked the first injector on the driver side, turned the fuel pump on, and cranked it from under the hood, I noticed that it tried to "hit" a couple times, so I tightened the line, which did pump fuel. I tried starting it again, and I could tell it was going to start by the way it was cranking, but it took a while before it finally lit off, it ran rough for a little while, then settled into a somewhat erratic idle, it ran for about two minutes, then died. I started it again, and it started a lot easier, then I started bleeding the injector lines as it idled, it smoothed out a lot, but still has the random misfire, I haven't driven it again since I did that, but like I said, the random misfire goes away at high RPM's, and it does NOT smoke at all when I hold it a steady high RPM, I did see two of the injector "O" rings were leaking slightly, but I think that happened after I loosened the fuel lines, the injectors look original, any way to tell, does this sound like bad injectors, or maybe an injection pump? The Thermo King pump has a clear sediment cannister and it is getting plenty of fuel, but I do see a small amount of rust looking sediment in the bottom of the cannister. I had another 93 non turbo that had a couple injectors lightly leaking, but it didn't affect the way the engine ran at all. HELP !!!!?????