Alright the good news...

The car runs fine, the brakes work, and the AC works. I replaced the small plunger type switch at the ignition when the problem first occured, as the old one was messed up. The car turned off perfectly...several times.

Drove to work, car turned off fine...no problems...

I drove home, and now...won't shut off. At all. Won't even stumble itself down. The switch I installed worked when it was isolated outside the car...that is, when the spring was not compressed. Basically the ignition tumbler depressed the metal switch, allowing the car to start. When the tumbler is turned left, to turn the car off, the open area allows the spring to pop out and shut the engine down. This worked for 75% of today.

I drive home, get home. Nothing. I am going to clean out the switch and associated plumbing again, but short of this what the hell could it be? There are only two lines that go to it. Baffling, but I will sort it out...I hope.

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http://www.betten.mercedescenter.com...n_banner_1.jpg
1976 300D
190,000 Miles
Colorado Beige

1975 300D
Parts Car
78,000 Miles
Rustbucket
Also Colorado Beige

1984 190D 2.2 (Dad's)
156,000 miles
Champagne Metallic Clearcoat

ttt bumparoo

__________________
http://www.betten.mercedescenter.com...n_banner_1.jpg
1976 300D
190,000 Miles
Colorado Beige

1975 300D
Parts Car
78,000 Miles
Rustbucket
Also Colorado Beige

1984 190D 2.2 (Dad's)
156,000 miles
Champagne Metallic Clearcoat

Do you have a mityvac?

You need to trace the brown vacuum line coming from the four way splitter under the hood. There are two brown lines, and they have different colored stripes to help you determine which is which. One goes from the splitter through the firewall and to the tumbler/ignition switch assembly, and the other goes from the ignition switch assembly to the shutoff valve on the back of the IP.
Once you find the shutoff valve, pull a vacuum on it while the car is running to verify it is still working. From there, you can try pulling a vac on the switch where the line from the splitter would connect, to verify that the switch is working correctly.


Chances are that you have a disconnected line somewhere. The switches rarely have problems (although it is possible).

The one thing that is key to understand is that the switch blocks the vacuum while the car is running, and opens when the car is turned off, allowing the shutoff to be evacuated and the car to stop.

__________________
1984 300DT turbo 138k mi

Still hauling me to school and back.

Handy Site:
http://www.dieselgiant.com/