Chevy Silverado cranks no start
 

I have a 1999 Silverado 5.3 that died one day after a 200 mile trip. Truck cranks but will not start. Removed plugs replaced with new ones. Check fuel pressure with ignition on 55 psi, while cranking 50 psi. It does run for 3 seconds with starting fluid. Drained fuel tank with tank pump and found some water. Put in Heet dry gas then put 2 gal. regular gas. Listened for clicking of fuel injectors and they seem to be getting a pulse. Have not checked them all with a noid light. Now I am at a loss. I don't know what to do next. Any ideas?