Vacuum Issue on 84 500SEL
 

Last week I replaced the plenum boot on my euro 500SEL. There was a small vacuum part attached to the side of the throttle body and has 3 ports to it. I was able to replace it with a part from the local MB dealership, and ran the vacuum lines according to the diagrams that the dealership had given me.

The issue now is that the vacuum line to the warmup regulators top chamber which is supplied by a line from the right side of the manifold and is also attached to one of the thermo swithes. The thermo switch indicated in the vacuum diagram is also joined to the 4 way junction that attaches the idle advance. This portion is already supplied vacuum from the top left of the manifold. The part I replaced is called the fuel injection vent valve, MB#003-997-00-36.

My issue is that I'm recieving vacuum advance all the time rather than on acceleration. Even when the system is hooked up accordingly and the other vacuum is not attached, there is no vacuum on the timing advance.

Does anyone have a suggestion? I've been at the mercy of some shady independant shops who have "screwed" around with the vacuum lines, so I'm trying to rectify the issue myself.

Thanks.

Euro 500 sel vacuumlines
 

AH! the key is EURO!!. The Euro throttle body vacuum switch has only 2 connections (I had one so I remember it well). Yours may have been modified to 'EPA' requirements which added EGR. It's supposed to have vacuum advance when off idle, and also when at idle and the coolant temp gets too high(that's the 2nd temp switch).

The other vacuum port on the TB switch of the US version feeds the control signal to the charcoal canister purge vacuum switch. (does not purge when at idle) Vacuum for the fuel pressure regulator comes directly from intake manifold.