1993 Dodge 250 diesel, won't start?

I started the truck for work, in the morning and everything was fine. I went to start it on my lunch break and it won't start. It was acting like the battery was dead, so I had the battery recharged at a shop and the battery is fine. I hooked it back up and the truck did the same thing. It is spinning the fan about a quarter of the way when I try to start it and if I turn the key at a rhythm it will continue to spin it a little but it is acting like it doesn't have enough juice to turn the engine over. The starter is the original I think and the battery has 850 cranking amps and 730 cold crank amps...the glow plugs are pretty new and the oil is changed regularly. I just can't figure it out. Advice?