Starting problems

If the engine is not getting fuel, there are a few possibilities to look at;
Clogged lines
clogged filters, (Even though you got the pump screen filter, some trucks have a second one)
The main relay
Fuel injector resistor, (your vehicle may have this resistor built into the fuel injectors)
The fuel injectors may be clogged and or failing
It is unlikely, but the trucks computer could be bad.

The fact that the motor will run when you dump gas down the intake also leads me to believe that the list of possible suspect issues are a good place to start.
Also check the fuel lines for cracks, (you would probably smell gas if this were the problem)

Let me know if you need any more help.