Looking for switchover Valve and EGR explanation. 1983 300D

[Doug183]

Hello,

I have an 1983 300D.

I have been troubleshooting some transmission problems recently that are now solved. In the process, I have eliminated the vacuum to the switch over valve system (box mounted on top of valve cover) and thus the EGR valve as well.

I know people recommend disabling the EGR system, but I would like to make it operational again. I have the vacuum diagram for my model, and can physically hook it all back up. What I don't have is any explanation about how the system works and what vacuum levels I should see at various points. The switch over valve seems to control two systems:
1) the EGR and
2) Reducing (I think) the vacuum seen at the vacuum control valve (the plastic thing on top of the Injector Pump that controls the signal to the transmission.) I assume this is for smoothing up shifting or down shifting.

1) For the EGR system, there are 2 points to measure:
a) From the switch over valve to the electronic temp switch: With the engine off and cool, should the line from the switchover valve to the temp switch hold a vacuum? Mine leaks slowly. What about when hot?

b) From the other end of the temp switch to the EGR valve. Should the line from the switch to the EVR hold a vacuum? Mine doesn't at all.


2) For the vacuum control switch:
What vacuum levels should I see in the line from the switchover valve to the vacuum control switch (intake)?


Thanks
Doug