Hi Shaun

'Difficult to decide on a direction with this one,'

Having no codes or much data always knocks my duck off too.

I know evantually you are going to need to communicate with the ECU even if just to clear the codes but for now if you scope the FRPS, Cam and Crank and put an amp clamp on the injectors.

This will give you alot of info and will most probably give you a direction to persue.

'I would love to know what the scaling factor is for the fuel rail pressure sensor'

Me too

The FRPS is generally easy to get to on most CRD (granted not all) the best thing to do is scope every CRD that comes through the door and get the CAM and Crank too (if time permits)

scope through IGN on, crank and start, idle, WOT, idle, IGN off. You will soon get a feel for different systems. Also it can save you loads of time in the future.

You can, most of the time help to split the fuel system in half and aim your testing in the correct direction.

I have been caught out more times than I would like to admit with dodgy fuel in the fuel system mostly Petrol

So now with a non start the order of testing for me is
FRPS profile (it is normally quickest and easiest)
Quality and Quantaty of fuel
Low pressure circuit
Then
High pressure curcuit

hth
James