Other than replacing your van's filters, it could be that the system is drawing air somewhere along the line, as most diesels are, nowadays, self priming, there could be a flexible pipe that is drawing air into the system, which is more apparent when the system is stressed. If you can bleed the system, check whether there is air being pumped out, which would indicate that it is sucking air, somewhere. Hope this helps.
davidj
August 2011
could be filter head diaphragm porous.
k
August 2011
Fit new leak-off pipes.
dieselbob
August 2011
you maybe better off putting an inline fuel pump (battery powered) on your van,had same problem with vectra diesel this cured it
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