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New Owner 1975 450SL vacuum port question

8K views 9 replies 6 participants last post by  cushjbc 
#1 ·
Hey Guys, I had no idea what kind of history this model of car had before I got it. There is an amazing wealth of knowledge here, really.

This car has had a full emissions delete apparently; air pump, diverter valves, switch-over valves, main vacuum switch, egr valve and charcoal canister. No idea who or when but its all gone. So for the majority of the past 2 weeks I have been tracing out vacuum lines, completely confused, thinking I was just really stupid and wasn't looking in the right location for certain parts.

I ended up sending all 8 fuel injectors to WitchHunter to have them rebuilt, ordered all new seal kits, replaced all the fuel lines under the hood, replaced the vacuum hoses to the AAV, cold start valve, and the intake housing, ordered new spark plugs & wires, distributor cap, rotor, and points, etc. All of this based on info here in the forum, I appreciate it.

However, currently the vacuum advance vacuum connection is connected to a random port on the manifold not the intake housing. I've looked through all the vacuum threads and pics, this particular port seems to be elusive and just out of sight in most pics. I did find a pic from FCP Euro on here that has the port connected to a green line but appears to just end. I am curious if anyone has any idea what is actually supposed to be connected to this port? I attached one of the pics from FCP Euro with a red arrow pointing to the thing I'm talking about. Any help at all would be appreciated!

Glad to be here.
 

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#5 ·
Rowdie is 100% correct. FCP published an article that had that picture in it and it is totally incorrect. I advised them of that and I believe they pulled that picture.

If you search here or look at the shop manual that is available on-line, you will find that the fuel from the pump is directed to a position between the two fuel banks near the front of the engine. From there it splits and flows down each bank and recombines at the fuel pressure regulator. From there it goes to a fuel damper and from there back to the tank.
 
#8 ·
Welcome to the forum I have a 75 also and may be able to help. That vacuum line you are showing on my car goes to a bank of solenoids on the passenger side next to the radiator, this controls timing advance and retard. it sounds like on your car all this hardware may have been removed. What does your distributor look like? Does it look like the one in the photo? If so I would run that vacuum line to the inside port of the vacuum can on the distributor that should be for advance I don't think you need to worry about retard and I would just block the other port on the vacuum can.
 
#10 ·
Have a look at these articles from the M117 Service Manual. I have another one, 14-050 that is too large to post here. Happy to send it to you via email if you PM an address to me.

It seems the ignition advance and retard function in 1975 used a vacuum source at the throttle body (2 ports at rear, 1 at front in 1975) as it did in previous years. The hard lines were not green for this function, they were white. If you look at the vacuum diagrams in the articles, green lines were related to EGR. 1975 was the last ditch attempt to make D-Jetronic environmentally friendly . . . CIS injection started in 1976 on the M117. Your car had the most advanced / complicated set of controls to manage emissions - probably frustrated a previous owner who elected to eliminate it all.

Don't know your intent for the future of these systems on your engine, but I would cap that green line until you decide what to do with it. Pictures of your engine will help in this thread as you proceed.
 

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