renault kangoo wont start?

Hi, asking on behalf of my dad, who is goin crazy trying to figure this out, he has a 1998 renault kangoo 1.9 diesel, was fine then one day it just cut out when driving, he bumped it and was fine, got home parked up, next day would not start, he has tried loads from me googling online, he has fuel to the fuel pump but no further, seems to be the stop solenoid on the pump thats the problem, someone said it could be immoboliser so we have done all that and thats fine. Any idea whats happened to this solenoid and what he can do to fix it, he was a mechanic for many many years but on petrol, so not familiar with diesels, this is doin his head in, someone please please HELP.
Thanx,
Emma