It's time to stop and take a deep breath and look at what we have.
First, no power to the fuel pump.
Second , running a separate power line to the fuel pump and it still won't operate.
The second item may be caused by a poor or none existent ground for the fuel pump motor.
The pump may be shorted and causing the power feed to it to open a wire or overheat a connection.
First the ground side of the pump has to be found and checked for a good connection.
If a direct line of power from the battery is connected to the power side of the pump plug, ground being good and verified as good, the pump is NO GOOD !
It either works or it does not.
The unusual part comes in as to why there is no power going to the pump when the key is first turned on.
The PCM makes the ground for the fuel pump relay to energize for that first 2 seconds. The idea is to make sure the relay is coming on for that 2 seconds. If not , the reason needs to be found before going any further into any other part of the system. Do you know how to check for that part ?