Does anyone have a good way to troubleshoot the door locks. It looks like there are 3 vacuum lines, Yel/Blk to the tank in the trunk, Yel/ Red - door locks?, and Yel/green door locks?

I've isolated the lines one by one, and can only get the engine to shut off if I cap off the Yel/black (indicating a leak). But the tank is holding vacuum. Is there something else that is controled by the yel/blk somewhere forward of the trunk?

A good diagram would be helpful.

Many thanks!

 

I don't know if this is good way, but it worked for me on the 83 wagon.
You already checked that the leak is on the locking system. The connectors for the lines are under floor carpets. When you pull the driver carpet, you'll find connector for driver door, lr door and line going to the rest of the locks.
From here you can troubleshoot the leaks.
Next connector is under passenger lock and next was under the rr seat. Don't forget about fuel door.
The leak I was able to find was on the vacuum "cylinder" inside the door. The upper rubber cap rotten and didn't hold.

 

Hmm. I am assuming from your post that yours won't shut off when the key is turned off. I have the same problem with my '81 240D. The initial diagnosis was the shut off diaphram. However, my door locks lose vacuum after the vehicle has been off for several minutes, indicating a loss of vacuum. I was under the impression that the lock system ran off a different vacuum system than the motor components. In other words, there are supposedly two pumps, one in the engine compartment for those components, and then one in the trunk for doors, etc. I haven't picked up a shop manual yet, so can anyone confirm the existence of two pumps?

Bud

 

if you got VIN, then maybe i got it.

 

I solved the problem......In response to the previous post, there is only 1 pump. It runs everything. The solution to my problem was a leaky vaccum valve located on the valve cover.

I should explain the engine not shutting off as a symptom of the door lock problem. If the vaccum drops the door locks will not work, and the engine will run a long time before it shuts off. The cause is definatly a vaccum leak. An easy way to test if the door locks are leaking is to pull up the drivers floor mat, crimp the rubber vaccume line connectors (1 lock/1 unlock) with some forcepts, and turn off the key. If the engine stops right away, one of the door lock units is leaking. If not then the vaccume leak is somewhere else. Mine turned out to be the vaccum valve, although I was suspect of the vacumm valve on the ignition switch.

A hand operated vaccum pump really makes isolating a leak much easier. Pump one of the lines down, if it holds, no leak!