So... I, the IDI guy, finally bought a Powerstroke. This truck, a white 2000 F-250 4x4 CCSB 4R100 truck, marked as "crank no start" came up at auction. 226K Miles. It all looked intact, so I decided to take a chance on it. $1800 later(2K after taxes and fees), it was mine! Now... Get it home, put new batteries in it(both were at 5V), cycle the glow plugs and... she cranks fine, sounds like she's trying to start on one cylinder... but won't pickup and go. No clouds of smoke. So, I grab my handy can of Engine Destroyer(ether) and... she fires up for a few seconds sounding "normal", before dropping down below idle and dying as she runs out of ether, with loud clacking as she does so(If you've ever heard a 7.3 running on 4 cylinders, you understand what I mean by loud clacking). A few more tries, checking a bunch of stuff and... nothing. Wait for a bit, figure on taking a video of it cranking to post online... we crank and she fires up! This attempt didn't even use any ether. Now, she's running, but on 7 cylinders and no power. Back it off the trailer, take it out for a short drive... floor it and as soon as the RPMs hit about 2100 it... takes off. Turbo spools and it just goes! Back to idle and it's running great. It runs good throughout the evening, warm starts happen without issue. That was two days ago. Yesterday morning, she was very hard to start but finally started(no ether). Rough and no power until I hit the road and floor it... get it up to 2K and... off she goes! Drive it to work, park, starting it after work was a little loud, and again stuck on 7... get it under load at 2K and working fine again. This morning was colder. Above freezing, but cold. She... did not want to start at all. Bring out the ether and as I'm giving her a thin spray while cranking, she lights off, revs up... and back down and dead. Repeat twice until I actually just sit there feeding it ether to keep it running(Note: my friend was in the driver's seat with the pedal floored the whole time) until it finally "catches". Repeat the 'running on 7 until loaded above 2K rpm'. So... I'm trying to troubleshoot this problem now. Once she's been started for the day(and "unlocked" by hitting 2K under load), she runs quite nicely. Oh, and I'm not seeing any codes. I'll have to check again, though, but I didn't see any codes(aside from KAM code due to batteries being disconnected) two days ago, and that didn't come back. I've checked: 1. Fuel filter looks clean, don't think that's the problem. (especially as it has plenty of power when warmed up) 2. Oil was recently changed - was still clean enough on the dipstick to see through. Changed by PO back in May, according to writing on oil filter. 3. Glow plug /relay/ was replaced, and seems to be clicking. Not sure on the glow plugs themselves(could well be dead). What other tests should I do?