Car is an 81 300 TD. About two weeks ago it quit shutting off with ignition. I found if I held key in door in lock position, it would choke out the engine. I have all four door panels off now trying to find the vacuum leak.

I have narrowed it down to the yellow and 'green' vacuum tube, because if I shut off ignition and crimp any green tube connector the engine will shut off.

Here are my questions. Where do the door vacuum tubes start from? Do they come through the firewall or is there some other starting point inside the cabin.

How can I isolate this leak? I really don't know where to begin tracking down the leak. Thanks
John

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1981 300TD
1985 300TD