XUD Starting Problem

[Doggy]

I have a problem with my brother's 306 1.9TD which, I hope, someone can explain, or provide a hint or two....

It has a Lucas pump, (1998/R with, I think, 2 solenoids - one accessible from the front with normal 12V supply and a second, under tamper proof cover, with integral power transistor module linked to immobilser circuit).

Am I right in thinking the accessible solenoid valve is there to control the pump output, i.e. enable/disable the 3rd cylinder?

It seems it wont start unless this valve operates, but that the 'tamperproof' one actually shuts off the fuel to stop the engine.

I assume it is turned on to maximise fuel pressure for starting then turned off except when maximum power is needed?

I'm 99.9% sure the starting problem is lack of fuel. It always turns over at a reasonable rate, the glow plugs are OK, it's just as likely to fail to start cold or hot. When it's behaving it's a really good starter for an XUD, starts easily without waiting for the glow plugs if it has run in the last 2 hours or so.

I'm now thinking worn pump, low fuel pressure. How can I check?

Appreciate any suggestions.