Vacuum line schematic

[maximumbob]

June 15, 2006

I am in dire need of the vacuum schematic for a 1981 300SD. I have seen the schematic posts at this site but am not positive they exactly apply to this 300SD. I am concerned with the correct lines to the two connections on the vacuum control valve on top of the IP and the one line to the side mounted vacuum control unit on the PI.

The second time I attempted to install a new vacuum control unit, the engine ran all out normally indicating an incorrect installation of the lever on the vacuum unit. However, I wonder if an incorrect vacuum line connection, or missing line, could also cause an engine run on.

I will not try to start again until I am sure the unit is hooked up right and the vacuum lines properly installed.

I really need some help as the car has been sitting for a couple of weeks.

If some one is willing to help, would you not only post to this site but send information to rbrown@texasbar.com.

It would also help if there is someone in San Antonio with an 81 300SD that would let me look under the hood. However, come Monday, I may be gone for at least a week.

Thanking someone in advance.

Maximumbob

[MattBelliveau]

Just so you know, the schematics on this website are pretty much universal between the w123 and your model vehicle. I think the only real difference would be in the central locking system, which I believe is a seperate system with its own vac source on you car (but don't quote me on that).

[Brian Carlton]

Originally Posted by maximumbob

The second time I attempted to install a new vacuum control unit, the engine ran all out normally indicating an incorrect installation of the lever on the vacuum unit. However, I wonder if an incorrect vacuum line connection, or missing line, could also cause an engine run on.

I will not try to start again until I am sure the unit is hooked up right and the vacuum lines properly installed.

The installation of the vacuum shutoff is the only determining factor as to whether you get the rack under control, or it runs away. Vacuum has nothing whatsoever to do with it. You can disconnect the vacuum line from the shutoff and the engine will run perfectly. The only issue will be shutting it down.

AFAIK, the standard vacuum diagram for the 300D and 300SD from '81-'84 will be the correct one for your vehicle.

All of the lines to and from the valve cover can be eliminated as they only control the EGR.