No expert here but this is my understanding of the system if it is Bosch CP3

The metering valve is on the hp pump and excess fuel is returned directly from the pump to the tank. IE only the required amount of fuel goes to the hp side and to the rail.

It might be an idea to check the return from the pump while cranking and see if it is returning fuel. Ideally you need to scope the imv to see whats it,s being asked to do.

As kevin said about 300bar is idle pres.


Is the original hp pump fitted or is it from the donor engine.