The van doesn't have glow plugs.
This is quite common on these 2.5Di engines, if the van is taking a long time to start it is normally due to the starter motor not getting full battery current due to a poor connection. You can solve this by removeing all the batter and starter connections adn cleaning them up and reconnecting them.
These is also another cause which is poor servicing or incorrect oil being used, replace the engine oil and filter and ensure the correct engine oil is used which should by 5w30 Semi-Synthetic.
MrMPuk
September 2008