Do you have a vacuum gauge? If not get one, or get one of the hand vacuum pumps with intgral guage. Then I would check for vacuum at the line that runs to the shut off valve. When you pull the vacuum line off the shut off valve, check for the pressence of oil. If oil present, the bellows are probably shot, and the source of your problem. If you show low or no vacuum at the line supplying the shut off valve, then you have a vacuum leak elsewhere and need to back track along the vacuum system.

__________________
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.