Vacuum loss
 

Although it's been a topic before, at the risk of redundancy, I'm wondering if I could speed up the process of discovering a vacuum leak(s). Does someone have an idea of the most-to-least common sites to suspect in my search. (1980 300 CD) I checked the pump and have good negative pressure that will hold after shutting engine off (while separating pump from system). I'm tired of having to go under the hood to shut her off.I may even aquire the use of other features as well. I'm down to basics now.

At a loss.
 

My '81 300D just had a week where it would not turn off. Somehow the vent line from the fuel inj. pump shutoff valve had clogged with a couple drops of motor oil. I used the mityvac to suck the oil from the line and from the shutoff valve port and it's back to normal. I have no idea how oil got in the line. Next time I service the injectors I'll check it out.

Instructions: Shutoff valve is white plastic valve on the side of the pump with two ports, one pointing up and one pointing out. The one pointing up gets the vacuum and the one pointing out is a vent. Disconnect the top line then connect mity vac and check if it holds vacuum and actuates. Reconnect the line then evacuate the vent port.

I did notice the top port (vacuum) on mine would gradually eak down when vacuum was applied. But it still works. I found one in the junk yard last week and will install it if I have any more problems. The unit from the junk yard looked fairly new and does not leak at all so leakage is probably not normal.