i have ls400 fuel pump went out replaced with new pump from dealer installed same as old one .still didnt work so replaced fuel pump relay with new 1 from dealer and fuel still doesnt work can some one please help me thank u mike

 

So maybe it's neither of those parts. What exactly does your car do (or not do?) And how was it diagnosed?

 

You can short out 2 pins in the engine compartment diagnostic socket to power up the fuel pump directly,maybe you should have done this 1st as replacing suspect parts by guess work is both expensive if the fault is still there and gets you no nearer a cure.
I would get access to a wiring diagram 1st ( CD ROM versions on ebay) then go from there,activate the fuel pump using the shorting link method described above then listen if you can hear the pump running.
You need to determine if the cause is electrical or mechanical ( fuel filter clogged?) before spending more money.