Damn, just bumped into this old thread, if the car is quite a few years old then you will probably find that the high pressure pump has expired. My Passat one died when the car was almost 8 years old, a new pump is not very expensive - but make sure the dealer sells you the new connector if your car needs it (pump connector has changed and so the car side cable connector needs changing - or at least its backshell - a pins out job.)
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