Pump timing is out bud. Your meant to use a dial gauge and can be quite tricky to set up.
If you've replaced the pump belt and now it want start, timing of the pump is your issue.
your pump belt may well be correct after fitting but you will now have to set the pump up correctly by turning the pump back and fourth slightly to time the injection of the pump.
cheeseman your right,
by loosening the cam pulley bolt you can turn the cam pulley and pump pulley without having to remove the belt.
The dial gauge is really only to fine tune but yes it does sound like the pump was not locked up before replacing the belt.
do as cheeseman said with the spurt test and your be able to get the pump timing close.
disregard the above post. if you have a 2.4 tdi then thats what you would do, but then realised you have a 2.5 in which then you adjust the two tensioning pulleys to adjust timing and vagcom to read MVBs. my bad sorry.