1991 Camaro RS fuel problem

Ok when I got the car I was told all it needed was a fuel pump. So I replaced the fuel pump ran fine for like one day. Then the next day went out side to start it and it didnt start so I listened for the fuel pump to hum no hum so I droped the tank again thinking it was something I done wrong with the wiring well nothing wrong. But still no start. So I tryed the relay. Nothing. Ecu. Nothing. Oil pressure sensor. Nothing. But see here is the thing if I undo the positive wire on the batt let it reset the ecu then I will start but only for a sec and thats if the fuse is in the bypass. So I dont know what to do can anyone help me here?

PS:1991 Camaro RS 3.1 V-6