http://bp3.blogger.com/_p71v9ofBM6w/R5ZR4hrNUFI/AAAAAAAAAIQ/XCBQ40qtPDQ/s1600-h/fuelflow.JPG
I believe you are talking about line #6 in the diagram? It is a return line with a check valve at the IP (17mm part). Dumps into line 8 along with 7 (return from inj's) back to the tank.
Check the path (especially 2-5) and make certain everything is in the right place. If it is, pull the top of 4 or the bottom of 5, and see if fuel comes out when cranking. If it doesnt, the lift pump may be bad (can be rebuilt). If it does, it could be a leaky SOV oring or bad SOV.