what would cause the injectors not to inject fuel?

 

-no fuel pressure in system
-calculated pulse width = "0"
-no ground provided by PCM to fire the injector
-injector burned out
-injector plugged up
-PCM not seeing low res Opti pulse pattern
-injector fuse(s) blown
-injector harness connectors not connected
-incorrect injector impedance

probably a few more.... but that's a start.