My 96 chevy Silverado 5.0 L vortec cranks but wont start. I replaced the gas pump and you can actually hear the pump working now gas runs all the way to the throttle body but will not take the gas. I spray a bit of starting fluid in the throttle body and it starts for a little bit then it dies. ive replaced the fuel filter and checked the following: spark plugs, distributor cap and rotor, fuel filter and they all work but the psi on the fuel pressure only goes up to 20 psi...it should be on 50-60 psi.... any answers to what it could be or what I should do sense I barely bought the fuel pump yet the psi is at 20? I really need answer please thanks in advance.