If I were you, I would see if your 1985 had the trap oxidizer replaced under the recall if you don't already know. Nobody knows how the vacuum is "supposed to" go as they have all been extensively modified through repairs, so I'm not sure a photo would help. If you haven't already done a diesel purge, I would recommend that as well as replacing your large fuel filter and the air filter.

It would help to get more info on the symptoms...

Dkr.