I have recently been doing my own 240D-300D diesel research, and it looks to me that you have quite a few bits missing. Check out:
http://dieselgiant.com/mercedes_diesel_maintenance_tips.htm
http://mercedesdismantlers.com//diesel_vacuum_system#Diesel%20Vacuum%20System%20Troubleshooting
do a Google search on 240D as well. Something to think about is setting up a consumer account on AllData.com, its poorly structured, but I have been able to get some reasonably helpful info for our wagon, including diagrams.