85 300TD vacuum problem

[Jatimo]

Hello folks.

A couple days ago I bought my first MB, and 85 300TDT. As you might expect I'm working out some vacuum system issues. Looks like I'm going to have to do an item by item inspection, as pretty much every vacuum subsystem is losing pressure when isolated and tested.

Is there a good reference on what the nominal readings should be at various points of the system?

Also, should my vacuum gauge be giving a steady needle reading just after the VCV? Its oscillating so quickly that it creates a nearly solid arc (as seen by the human eye) with about a 5 inch Hg spread. I ran out of daylight today before I got to check the the pressure directly from the pump.

Could this be a sign of a worn rubber diaphragm in the vacuum pump or fault in the VCV?

The shutoff valve was previously disconnected completely (as well as the transmission tube after the transducer), and oddly there were no free hoses or connector points. I added a T-type connector to the appropriate line after locating it with the MityVac and hooked in the shutoff valve and the engine stopped as expected when key was turned off. but this had the unfortunate side effect of causing the engine to not go above 1.3krpm or so, no matter how much throttle is applied.

Faulty shut off valve, partially engaging, or perhaps I installed the fitting wrong? faulty engagement at the ignition assembly, causing partial engagement of shut off valve, and starving engine of fuel for higher rpm?

possibly related, the vehicle might also have low power at low rpms, but its hard to gauge at this point because its my first diesel, and the accelerator has a lot of play in it until i install the new bushing against the firewall.

Thanks in advance for your suggestions, and for your past postings, which gave me the confidence to buy this vehicle in the first place.