1997 Chevy Express Changed fuel pump. Ran for a week and di

Hey guys, I installed a aftermarket fuel pump in my van. At first I couldnt get it to pump gas, it would only pump air. I removed the fuel pump cannister and fill the bottom cup with fuel and reinstalled into the tank. After the engine turned over a couple times it fired right up. I drove the truck for a week, about a 1/4 tank of gas used. Now, wont start again. I took the line loose where it close to the engine and put a rubber hose on it to see the fuel coming. It only pumped a few inches of fuel into the hose. I have very little fuel pressure. Any suggestions? Ive def. Got power there, you can hear the pump running for two secs upon key on, then it will continue to run a few secs after I stop cranking the motor. Please advice ye great ones ;o)
Michael