[Andystobbs]

Why not unplug all four injectors and monitor high pressure? The system should still aim to generate 150bar and with the injectors disconnected they can't open and reduce the pressure, obviously it won't run, but it isn't anyway.

I can't remember off hand how the HP volume is controlled, ie. whether its 2 wires directly to the ECU or 1 to power and 1 to ECU or 1 to ground and one to ECU.
The system is actually capable of running in classic injection mode under certain circumstances, at 5bar pressure as provided by the LP pump.

EDIT *sorry my phone didn't display your entire post and I replied before scrolling, not even realising there was more. What pressure did you see with the injectors unplugged?

With no fuel demand the rail pressure should increase very quickly during cranking. The cam is trilobal so you get 3 pump events per cam revolution. It should be up around 150bar in no time at all. Is there a parameter for HP flow control signal?