Any idea what this is?

[Hartzpartz]

This component is on the LH bank (n/s) of my 1991 500SL (R129). It seems to have an electrical connection and a thin vacuum pipe going to the underside. As you can see, it sits above the injectors on that side. The black 'knob' or blank rotates but doesn't appear to do anything. There is a graphic on the front of the bracket with '1', '2', '3' in little circles that are connected by lines. Just curious to find out really.

 

[carat 3.6]

Vacuum valve, releases vacuum pressure from that part of the system.

 

[Hartzpartz]

What part of what system?

 

[carat 3.6]

Cars with the old ke-jetronic fuel injection system like yours use vacuum pressure to control various parts of the system. There is a system of small pipes to route the pressure around the car, sometimes it needs to be vented which is what that valve will do..

 

[Hartzpartz]

I see. So basically an electronically controlled vacuum line vent. Thanks for taking the time to reply.