Posting these photos and diagram of the Piersburg Fuel pump in case anyone else runs into the same problem as I did. i found a photo of when I pulled it apart and springy flap thing is clearly closed.
Not so clear in diagrams…
Mine was definitely open when I rebuilt it- hopefully the cause of problem.
Thanks for all the help.
Will let you know how it goes
Install a US made FACET electric pump and you have instant fuel pressure when the ignition is on. You have a tidier engine bay with one less fuel pipe and a deleted/blanked off mechanical pump.
Got the original sorted. Sucks like a ……
Let’s just say it’s working well now. Like a new one in fact. Thanks for everyone’s help on that as was a simple fix in the end.