D6N no start

I have a D6N that blew a return line off while running. Found the leak, easy fix. The engine will not start now, after much bleeding, all three fuel filters replaced, more bleeding and nothing. I do seem to remember that after reaching pressure the electric lift pump would usually change sound, "labouring" if you will, but It does not seem to make pressure like that anymore. this is a DJY1000ish serial (i cant remember exactly now, no more than 1100) Now similar used to happen on the old HEUI's with the pressure regulator behind head, but this is a HPCR engine. My biggest question is where is the low pressure fuel regulated? and could this have failed causing the big dump of fuel, pushing the return line off? With the electric primer I have big volumes of fuel at all filters, but can't get fuel out of the High pressure rail. Not a drop. Any experienced ideas appreciated!