Pull the air intake...the tips of the compressor blades will tell you a lot as to how much dirt the thing digested...unless the turbo was replaced, which could also be a good indicator of deeper problems. Ford did not build a very good air box and most people do not change air filters. If at all possible, start the truck cold, wait on the glow plugs and if it fires right off all is good, warm the engine to full operating temp then shut it off and wait a minute before restarting, if it starts ok the fuel system should be good.