I stalled Diesel Fiat Multipla (2002 JTD), would not re-start,?

Checked for diesel by slacking off feed to injection pump,
Ok, checked flow return from injectors, initially some air. diesel mix, but immediately just good flow of diesel.

AA man ( a very , very nice man !), suspected camshaft sensor, as diagnostics showed this reading absent, however FIAT garage( Nr Bognor Regis); changed sensor -to no avail ! ! !
I'm NOT a mechanic, though I suspect this might be due to the "shock" in the fuel line / system when the car stalled.........( I'm thinking - Pressurisation, then suddenly, there's nowhere for this pressure to go ??? )
Any experience of this out there , please ?