can anyone help with a 73 240z fuel system diagram ?

The electrical system has 2 sub-harnesses(passenger kick panel) that power the pump only when the key is in the run position and the engine is NOT running.

The original harness only operated the pump to PRIME the system. This is very helpful when the car has been sitting for several days or on hot climates where heat has caused the fuel in the lines to vaporize, vapor-lock.

This means that you must still use the mechanical pump to feed the carbys on a car with a stock electrical system.

If you are looking for fuel pipe routing then:

One is a LARGE feed tube(right frame rail to filter area)

one is a SMALL return line(right frame rail to filter area)

one is a SMALL vent line(left frame rail to vacume flow control valve)