Hi:

I have a 1984 300 Turbo Diesel and had a vacuum system question . . .

I've been doing some reading and have found that a number of people have removed the 3/2 vacuum switchover valves on top of their valve covers in order to deactivate the EGR valve.

I noticed there wasn't any such hardware on top of my valve cover (see attached photo), so at first I thought the previous owner may have done this.

However, looking at the vacuum routing diagram on the car (see below), I'm not seeing any vacuum-related line or fitting connected to the throttle. What I am seeing are references to an "electric vacuum control valve" (14.20) and/or "Electric switch-over valve-bypass (33.11) connected to the EGR valve.

Were the vacuum switchover valves typically seen on many of these cars online (mounted on the top of the valve cover, with the black plastic cam and white plastic levers actuated by throttle position) replaced with electric switchover units by Mercedes-Benz at some point for the model year of my car? Based on the diagram, it looks this was the case, but thought I'd ask all of you here.

Thanks,
Eric

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In 1984 there is a California version (do you have a large Air Filter close to the Radiator on the right side?) and like mine a Federal Version.

Someone who has a Clifornia model of your year will have to Chime in on that. Member Deliveryvalve used to have a California model but I don't know what year. You could contact him as he would likely know the info you need.

On the Federal Version there is only 2 of the 3/2 Valves and nothing is electronic. All the valves do is actuate or turn off the EGR Valve.

If on the right side of the Fuel Injection Pump is there a plastic or aluminum box with wires coming from it. If so that Box is a Rack position sensor and that is what controls the EGR.

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84 300D, 82 Volvo 244Gl Diesel

Found the attached diagram in my Notes. The read aroow points to a Calfornia 1984.

Actually there should be another sticker on the Car; the one that has the timing and valve adjustment specs. It will say if it is a Federa or Calfornia Car.

Also the California Care has a slighly different Transmission.

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84 300D, 82 Volvo 244Gl Diesel

Diesel911:
Thanks for the info. The car was originally from Alabama, although appears to have spent some time in Germany beforehand, possibly in one of those pick-up-from-the-factory and drive your new car on vacation deals.

Its EGR/vacuum setup does look a lot more like a CA car than anything else, and I'll treat it as such. Just hope I can find the electric switchover parts if or when they're needed. Thanks again for the information!

Eric