With the understanding that the vacuum pump source gets split off into two systems.. one being to the transmission shifting and the other to "other consumers"... will a leak in one system affect the source strength of vacuum going to other system? Or is there a buffer in place to prevent the two systems from affecting each other?

I have shifting issues, but also issues with very slow door locks. Planning to do a test of the pump first but wondering about this too.

YEs. Plug the line going to the other consumables. Then get your trans working. Then find and stop the leaks in the consumable circuit. There are 123 and 126 vacuum diagrams available online and in the FSM.

__________________
85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

In most cases it shouldn't. The most critical vacuum consumer is the power brakes. The other consumers have an orifice in the line to prevent losing your brakes should a leak develop or a line break. As long as your vacuum pump is reasonably strong you're good to go. If your brakes are weak check the vacuum pump.

__________________
Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
• Baja Bug
• F350 Powerstroke
• Auburn Boattail Speedster replica

This may help in the search --how to articals -- at the top of this page ^

I have a healthy 22.75 HG from the vacuum pump. Plugged off all connections and got a stable reading.
Engine had to be manually switched "OFF" after ignition key turning off didn't do the job. I assume it's part of the inter-workings i had disconnected but figured i'd post that here just in case that was something to note.
I would certainly like to be able to block off the door/trunk lock vacuum system from the rest of the vacuum system so that i can drive around and focus on the shifting/trans. I will investigate finding a point around the check valves for this. Maybe the two "c" points can be blocked and accomplish this.

All it takes is one rubber branch or vacuum actuator to leak, and pretty much everything will go. What you need to do is to start at the pump and follow the lines outwards. At each branch, block off one flow path at a time to see whether if the problem resolves on the other lines. Keep moving outwards, and you will quickly locate the leaker.

I disconnected this yellow split point/device which has the two yellow/yellow-gray vacuum lines going into cabin to locks. Is this just a splitter, this yellow contraption? Because if it's an actuator, it doesn't make sense according to this diagram.
If i'm interpreting the diagram correctly, those two yellow lines should be a pure split off of a single point after the actuator, rather than being connected to the two points of the actuator. So, hopefully that yellow device is not an actuator and is just a fancy spit unit.
Regardless, i drove it around after capping off the point which feeds this yellow device, and the car drove as normal although i believe i could detect a LATER shift in general. Not certain but i think so. Also i believe i could detect a more obvious shift into 4th gear when that happens.
One thing to note is that the locks seems to work still, albeit slower. Does that even make sense? The yellow device is still open ended. I kept thinking each time i tried the locks they would get increasingly slower and eventually lose their vacuum and stop, but they keep working just slowly. Maybe it takes 20 or so tries to lose the vacuum?
(edit: just want to also add that the open looking black rubber connection point is not actually open, it just appears as such because i was bending it and thats the edge of the connector. the tube going into it is solid and snug, you just can't see it here)

The yellow thing is a splitter AND check valve in one item. It is important to make sure you have no leaks. Any leak in the system will bleed the vacuum pressure level down, even with a perfectly functioning vacuum pump.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Now that i have the lock system isolated, i am going to focus on this step by step working away from the pump to possibly see if my shifting issues aren't vacuum related.
How do i expect readings to be... WITH everything connected (minus the lock stuff), AND if i pop on a splitter and a HG gauge, should i simply read the same 22.75 HG that i read when directly connected to pump while car is running and the pump is isolated? Or does my expected reading change depending on what is connected..
In other words, if i were to bring it back to just measuring the pump and incrementally add segments at a time to it, should i be always be getting 22.75 HG even if i am adding segments? Do some segments deplete vacuum by nature of their operations?
This is all with the throttle closed/inactive.

I expect the German Vacuum Principals to look something like this:

__________________
1982 300CD Petrol/Black Leather

When i lifted the hood for the first time these four gentlemen popped out of the engine and ran off into the field carrying synthesizers!

So i tested the modulator for ability to retain pressure and fortunately that is looking solid. Held 22 HG for well over a minute without budging.
But i also checked the venting valve and found that i wasn't able to get more than 12 or 13 HG on it. It just makes a farting sound and the device seems to vibrate when this happens. Here's a video of it, and also here is a pic to be clear about which piece i'm talking about...
The functionality seems to work.. it will very slowly decrease from the max pressure and if i start to open the throttle linkage it will increasingly let out pressure. So it seems to just not be strong enough but it still performs at around half the strength. How will this affect shifting?
...
https://dl.dropboxusercontent.com/u/4482480/IMG_5174.mov
...

i went and replaced the connections to the vent valve with new rubber and still the device is not able to go above 12 HG or so and makes that sound. I thought maybe it could be the connections/testing scenario but it's the valve i believe, leaking out vacuum levels higher than 12 HG.

More vacuum = softer shifts.
What is wrong with your shifting?
Have you adjusted the bowden cable?

__________________
1982 300CD Petrol/Black Leather

I would focus on the "won't shutdown" issue first since that is simple. Most commonly, the rubber diaphragm in the shutdown valve tears, which sucks oil in from the injection pump. Eventually, that will get up to the vacuum switch on the steering column and start dripping down the underdash cover onto your right foot. Install a tiny clear filter in the engine bay off the shutdown valve to monitor for oil. You can test the shutdown valve w/ a hand pump.

__________________
1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans