Duramax gurus??

[scotts62]

Well here is the deal if anyone has an idea to throw my way. I am working on an '05 3500 with a Duramax. The truck came in with a missfire and code for #6 injector so i threw one in and it was running fine for a few days then came back running rough again and the guys driving it said they think it got water in it because the fuel cap was off (who knows, real bright ones at work) It was low on fuel so i put about 3 gallons in it with some 911 treatment and parked it outside the door of the shop and let it run, i could hear it out there and it ran for over an hour and i went to test drive it and ran fine. Brought it back and let it run for a while longer and just before lunch i wentt to turn it off when it was already off, temp gauge was tacked out and coolant everywhere.... well turns out that the idler pully locked up and shreaded the belt.. i let it sit for a few days and got back on some other stuff we had going and have been trying to get it to start and it well crank but no starty. replaced fuel filter again, pulled the top off of the fuel tank (has a dump bed on it) and turns out it had almost 5 gallons of water so i cleaned it out and filled with new fuel and still cant get this dude to fire. Pulled the main fuel line to the fuel rail just to see if the high presuure pump was pumping and it was getting fuel out of it but nothing fancy pressure wise but it is diconnected so i didnt expect all that much. It will fire and run on starting fluid but i didnt want to dose it too bad. That is my cluster and if you have an idea id appreciate it.