How fast should vacuum build?

[tankowner]

I've been knocking off some projects on the 240D recently and now I have returned to the problem of not being able to shut the engine down with the key. In the past I had tested the SOV with the Mity Vac and it seemed to be fine . . . can shut it down easily with the hand pump hooked directly to the SOV. I had also taken some measurements to make sure the vac pumps was pulling enough vacuum and it will do about 21", which seems good. Those things led me to believe that perhaps the vacuum valve connected to the steering lock (operated by the key) could be bad. It seemed to test out okay, but I wanted to be certain, so I replaced it . . . turns out, no problem there.

So today I did some more testing - I placed a vacuum gauge in line between brown line that leads to the key operated valve and the main vac line coming from the pump. I removed/closed off all other line (HVAC, door locks, etc.). The only other line that was still attached was the main line to the brake booster. Note: door locks not operational, but I have never noticed a problem with the brakes.

So then I started up the car and let the vacuum build. My question is . . how long should it take vac to build up. It got up to 10-15" fairly quickly, but then it took some time (maybe 2 minutes) to reach 21".

Then I turned the key off . . . the vacuum drops down to next to nothing, but the engine doesn't shut off. Then the guage begins to slowly climb back up . . . after about a minute it makes it up to 5" and it kills the engine.

So it seems to me that the pump just isn't pulling like it should . . . but I also don't know how fast it should be pulling. Worn out pump? Bad seals? Other options? In my searching, I see that the check valve on the pump and can gummed up, I'll go check it out. Figured I would ask about the pump though and get some feedback. Thanks.