I have a 91n 300zx 2+2 and having problems with fuel system
The fuel pump runs for 2-3 seconds and stops. thus no fuel to engine
So far what I have done: checked fuel pump fuse in engine compartment, replaced relay for fuel pump in kick plate drivers side inside car, replaced fuel pump and and fuel pump assembly, drained and clean fuel tank, blew out supply and return fuel lines. What am I missing

Try to bypass your fuel pressure control unit, just look it up there should be a write up somewhere

I don't have the fuel line connected to the regulator so I could flush and no fuel is coming out ???

1. Are you sure you're looking at the regulator not the damper.
2. You didn't mention the fuel filter, has it been changed? If not, check for fuel upstream of the filter.
3. Are you sure the pickup tube and sock are installed correctly?
4. Is there fuel in the tank? If you cleaned the tank and put in a minimal amount of fuel you could be below the pickup.
5. If none of those it's likely the Fuel Pump Control Unit. Try putting 12V directly on the fuel pump contacts to see if it starts pumping fuel. Obviously electricity (sparks) and fuel don't mix so take the necessary safety precautions.

Thank you I will double check everything