1992 6.2 cranks but wont start

My teenage son has a 1992 Chevy K2500 6.2 diesel truck. We were hauling water and it surged a little then died. We haven't been able to get it to start since. It will turn over, but won't start. We have replaced the IP with a brand new one & lift pump. We were wondering if it was getting fuel, so we put a clear filter in the fuel line so we could see what it was doing. We have also bypassed the tank & line, putting a line straight from a can of diesel fuel to the IP and took the glow plugs out. We are getting a spray of fuel out of each glow plug hole. We put the glow plugs back in and it still won't fire. We also tried spraying a mist of high powered starting fluid above the intake holes and it still won't start. Any suggestions on what to try next?

Howdy
Fuel + Air + Compression = FIRE.....seems like the only thing you haven't checked is Compression...
Also is the timing set right...so that the fuel is entering the cylinder at the right time.

Checked glow plugs??? Unless the engine is hot or in really good shape, the engine won't start without some glow.

If you have a block heater,plug it in and it may help in getting it warm enough to start.
Thomas