I'm trying to get the vacuum routing on this wagon back to how it should be. Someone messed with it before and the transmission line was disconnected!

There also was no damper going to the VCV. I'm not familiar with how the non-turbos with vacuum controlled transmissions are setup, so I started to route it like my 82 300sd.

Note that one orifice off the main line is broken and I'm waiting to get a new main line. So, the IP shutoff feeds from the orifice that goes to the switchover valve and VCV, all other vac lines are disconnected. Also, I deleted the EGR.
I'm just looking for how the switchover valve, VCV and tranny should be routed.

Also, I'm having a little bit of flaring, which is partially why I'm trying to get this setup correctly.
The VCV only holds about 6 or 7hg and makes a lot trumpeting noise when I pump vac into it. I pulled one from a wrecking yard that holds 12 and seems more solid. Was going to swap it out, but wanted to make sure it wouldn't make the flaring worse?

Swapped it and it did make the flaring worse. It pulls 14hg from the port to the black tranny line and only goes down to 2.5 instead of 0. Going to adjust the new one down tomorrow. (accidentally left the old one on top of the car--flew off getting onto the Bay Bridge, oops!)

That is if I bypass the switchover valve. I found that with the switchover valve connected it only pulls 5hg so I bypassed that and went straight to the VCV.

What does the switchover valve do on the non-turbos? I know that the bigger one on turbos (that looks like it has 5 ports with only the top three used) is only about the functioning of the EGR. I bypassed that one on my 82 300sd with no problem.
Is there any problem with bypassing the switchover valve on the non-turbo?

Also, thinking of adjusting the VCV linkage as it usually shifts fine at lower RPMs, and the flaring is much worse at full throttle.

The switchover valve causes the downshift to first gear upon take-off, so best keep it.

What is the fuel filter doing in the vacuum line?

The vacuum diagram is in the FSM

14 Intake Manifold, Exhaust Manifold, Emissions Control System - OM617

work 14-050

See also the picture below.

The Y piece at the VCV needs to be placed at the switchover valve, so that you can make the blue connection.

Attached Thumbnails

 

The switchover valve leaks horribly and needs to be replaced.

The filter is to collect any oil in the vacuum line, I actually removed it but no matter.

I adjusted the new VCV down and the transmission is shifting a lot better now, even though it looks like the routing is totally off-spec.
Thanks so much for this link! Super helpful!

So the main vac line splits off to the tranny modulator and the switchover valve, which then goes to the VCV? The VCV is not inline to the modulator like it is on the later models/turbos?

Wait, I guess it is inline in a way, but just through the switchover valve.

I'll try to get a replacement switchover valve

Yes, it is inline, but at idle the switchover valve is closed so that the transmission gets the full vacuum of the pump. When you press the accelerator pedal, first the switchover valve is actuated, so that there is a connection to the VCV. Vacuum is reduced from -0.7 bar (pump vacuum) to -0.35 bar (VCV vacuum) and reduced further if you press the pedal further.

The little flipper of the switchover valve is often damaged too.

As I recall, there is a vacuum diagram for this particular model in the Haynes Manual. I have a copy at the shop and will try to remember to fetch it. Are you sure there is not a diagram on the radiator core support?

Whip

The FSM link posted by Govert above has a diagram.

Now I understand how it's supposed to be, but I can't route it correctly because the switchover valve is bad.

My daughter's less-than-optimal transmission performance could probably be traced to the unusual vacuum routing. A line runs off the main line to the 2-3 valve. Another line runs from the 2-3 straight to the transmission. The VCV is fed by another line off another tee on the main line. The VCV output is into the cabin.
I thought the 2-3 got the line off the main, and sent a line to the VCV, whose output was to the transmission. All other lines, fed off the second tee, went to other systems (CCU, door locking, etc.)
I swear one of these days we will have to cooperate on posting pictures of vacuum control systems that actually function so others can use those as a guide.
Are all the "orifices" shown in the FSM all the same inner diameter? There is a yellow one in between two wye connections on my daughter's 1980 300TD.
However, there is no green "damper" in-line between the VCV and the vacuum source. Then I am told that there is no need for this green damper on the 1980. On the third hand, the FSM shows what appears to be a green damper in-line above the VCV.
Confusing? I think so.
And no, for us the answer is not a standard transmission.
I imagine that once I can get this figured out, and the transmission starts shifting like a good transmission, I can post pictures of what it took.
Then I get to do the same on my 1981 240D, which has a similar but not identical FSM-contrary-type setup. Is seemed to shift OK, but not what I would consider a "good" shift.


so much fun

snapped_bolt

__________________
'81 240D For now, a good place to borrow new parts
'80 300TD Probably will be put back into service!
'79 240D BACK IN SERVICE SINCE 09/16; limited use, oil leak. Guide pin r/sealed/replaced. Still a leak. Front crank seal....

No they are not, but I think the yellow one is correct. There is a post somewhere that goes over all the different orifices.

I think how it is supposed to be is:

One connector off the main line to the door locks, climate control, etc.

Another comes off a little ways, then has a Y connector, with one line going directly to the transmission and the other going to the VCV via the 3/2 valve.
Since my 3/2 valve is busted I just had that one go directly to the VCV. Or rather, there's a Y connector on top of the VCV with one line going to the tranny and the other to the main line. It seems to be shifting just fine. Not perfect, but pretty darn good.

Also, regarding the green damper, I don't think it's stock on the 80 although I can't figure out why.
It seems to shift the same with or without.