Fuel flowing out of return line.

[Herbivore02]

Hi, what would cause fuel to flow through the return line coming from the high presure pump? Happens with the ignition on with no cranking and comes out faster when cranking. I think this is stopping my van from starting because the presure is only getting to just over 12000kpa when cranking.
2017 transit custom 2.0 130bhp euro 6
Just had both fuel pumps replaced with for original parts.
I did get it started today after bleeding the fuel lines a little but it was idling at about 1100rpm. Any help or suggestions would be appreciated