1982 Mercedes Benz 240d cruise and door locks do not work

My software doesnt go back that far for vacuum diagrams, but it does sound like a source problem. You can use carb cleaner to spray at the hoses, when you hit a leak the engine should react. If you can find where the source line is for the doors, you can access the inside of the doors and plug off the feed line, pump the other end with your vacuum pump and see if it holds, if not there is a leak. Check up nea rthe firewall on thedrivers side, if I remember correctly that is where alot of the feed lines are off the vacuum pump on the engine