We had the same recently in our 03 TDCI engine works van. It turned out that it was the pump(common fault) The symptoms were that the van wil knock like mad (liked if you fill a diesel engine with lazy start) My understanding is that the baearing in the pump fails and sends swarf allroud the fuel system causing problems with all associated componants.Pump, injectors,tank,filter head and filter. Just a heads up to Tranny owners.