Hi Mark.
I have not dead headed the pump. What I have done is earthed the IMV valve through a test light to see what happened. The pressure went up to 1800 bar ( live data,4.8V on the scope). This all happened @ idle. Is this enough to prove the pump?

I am thinking that the pump cannot supply enough pressure when under load because of excessive leak back from the pump (I am clutching at straws now).

Thanks.
Fiachra.