I have a Fiat Ulysse from 2004, type JTD (diesel). When accelerating the engine stops all of a sudden. This happens when accelarating in too low gear, e.g at 20 km/h in third gear, or 80 km/h in 5th gear. The garage dignosed that the high pressure fuel pump must be replaced. Does anybody have some experience with it? Is the garage right in its diagnosis? Can I replace it myself?