Just remembered a similar fault on a Citroen Picasso. The vehicle had either run out or had almost run out of fuel. More fuel was fetched using a container that had once held truck-cleaner (detergent) and this was a very bad mistake. It seemed that the traces of detergent left in the container reduced the lubricity of the fuel which is extremely marginal in any case, and the high pressure pump was ruined.

Fortunately a vehicle dismantler had a similar engine which had blown-up (big ends gone and a rod through the block) They don't normally sell the pumps separately but as the engine was scrap, this time they made an exception. £150 and the car was a runner again! With Common Rail, Hdi and all that stuff the fuel is really critical and some drivers add a trace of two-stroke oil which is legal to burn as fuel, in order to help the pump. If one does do this it is advisable to use blue two stroke oil and not the red to avoid any misunderstandings! The good news about Common Rail is that pump replacement is straightforward as the timing is done by the computer.

Without the proper pressure gauges and adapters it is not possible to tell whether the pump is producing 5,000 psi or 40,000 psi as "cracking" unions will just give a spurt of fuel.