Vacuum problem, '81 240D . . . .

2 days ago, when I turned the ignition key off, there was a bout a 2 sec delay before the engine stopped. Yesterday morning it was a second longer. Last night, it would not stop at all. I had to go under the hood and press the kill lever. Also last night, ALL the locks quit working.

I thought the shutoff valve was going bad. It would appear that there is a vaccum leak elsewhere. There has been no work done on the car in the recent past, so no chance of something having been knocked loose.

I was thinking of checking the vaccum pods in the doors first. I really don't want to tear the door panels off, mostly because I don't know how. Anyone have suggestions where the most logical spot would be to start testing for the leak?

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1981 240D, Auto Trans, 160k miles -- CRASHED!