my engine is hard to start sometimes, it will sputter

i have a 93 chevy cavalier 4cyl it was hard to start and kept sputtering so i figured i would change the fuel filter but when i disconnected the fuel pump relay and started the car to releive the pressure from the fuel line the car never died. So I figured I dont think its the fuel pump going out because I can hear it working when I turn the key all the way but dont start the car. The keys were completly out of the ignition when I took the fuel line off the filter