fiesta stalling again.

[bodgit]

Midway through 2012 my daughters fiesta 1.4 tdci started stalling . Diagnostics came up with crankshaft position sensor so a new one was fitted and 19000 miles later all was well until now. The thing is stalling again.
Booked it in for a full service and diagnostics showed the fuel rail pressure sensor was faulty. Ford wont sell one on its own you have to buy the whole rail £250 +vat. I soured a new sensor £56 and it was fitted and fault code cleared but it still stalled when they started it up they think it may have been air in the system as it seemed ok later when it drove without stalling.
Im collecting it tomorrow but if it plays up again does anyone have any ideas what else could be the cause