I just got the car. 1984 300d AT

The engine sounds and drives very good; smooth and quiet, scored really great on emissions, %3 opacity.

The problem: when warm, if I shut it off for more than a few seconds it won't start.

If I wait for about 15 minutes, It will then fire just fine with a bump of the key.

I have naarowed it down to a vacuum actuated valve on the top back of the IP.

If I unplug the vac from the valve it will start right up.
For some reason the vac and/or the valve are not acting right.

Anyone know what i should do with this problem?