1975 280z maybe fuel problem? Help please

I just swap out my rb25det from my 75 280z. I just install original l28 back into the car. Connect every wires to it's original location, even install back the oe fuel pump also. This morning before going to work I try starting the car, and their was no click on the efi relay. I got a light tester and check all main power connetor and got power. Came across a four wire(2 white 2 green) connectors under the dash from coming from the engine harness to the computer. There was no power from these wires! I then trace the power wires from the 4 wire and wire the 3 power wires into the key igintion wires and wire the last wire to the fuel pump singal to the original connector. Turn on the key and relay click but cannot start-up. I then disconnect the fuel pump singal wire and started it agian. Finally it fire up, but only for ten sec, n it died. Gave it another try and did the same thing. I think the car is lacking fuel from coming into the engine. I'm out of ideas now and don't no what to do. So anyone that had or have experience please give me advice and help out?