Hi there. New member here -Allen's the name. Great forum, been lurking in the shadows for years. Started when I had my '85 190E and now continues w/ my '79 300D. I hale from west-central Wisconsin.

Enough introduction, moving along to my problem. On my '79 300D, the PO had the vacuum system pretty hacked and I've been sorting it out to get it to be correct. I guess when the vacuum pump diaphagm went out he didn't want to spend the <$50 for the rebuild kit and proceeded to shadetree install an electric pump he must've had lying around.

On the top of the injection pump, located at the rear where the ALDA would be in a turbo car, I have this prob. 3" in diameter cylinder about 1" tall. Mercedes calls this a "Vacuum Box". It has a nipple coming out the side of it, I pressume to tie into the vacuum system somehow. I need to figure out what needs to be hooked up here. I think this is for mixture control? BTW, this car does not have the vacuum modulated trans -all mechanical linkages for that.

I do not have pictures now, but will probably take some tonight when I get home, or tomorrow.

TIA

Is this possibly the IP vacuum shutoff valve you are speaking of....?

Located on top rear of IP with a vac hose going through the firewall to the key operated switch pass valve....

Vacuum applied to this box pulls a lever inside the IP shutting off the fuel delivery....

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1978 Yellow 300D (The Mustard Toad)
1980 Blue 240D (The Iron Toad)
1989 Grey Mitsu.4WD Mighty Max Pickup (Needs a Diesel transplant bad)

(Open the pod bay doors HAL)

Nope, not the shutoff. That sits on the back of the IP, and mine is hooked up and functioning properly. The unit I'm talking about sits on top of the IP.

If what you are calling the "vacuum pump diaphragm" (shut off switch) is on the aft end of the IP there should be a brown vacuum line hooked to the nipple. There is a similar looking thing on top of the IP with a nipple that nothing is attached to.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Does this thing have linkage attachments on it...?....Possibly someone put an IP on there that came off a Vac controlled tranny 300D...

I have a 1979 300D........I can check it for what you describe when I get back to the shop....

I think you are looking at the thing that has linkage going into the IP governor system....Aneroid governor control or something along those lines....

__________________
1978 Yellow 300D (The Mustard Toad)
1980 Blue 240D (The Iron Toad)
1989 Grey Mitsu.4WD Mighty Max Pickup (Needs a Diesel transplant bad)

(Open the pod bay doors HAL)

There are no linkages to it. I also was beginning to think someone might have swapped the IP out at one point in time, but I had Mercedes (Sears Import) look this up according to VIN so I would know what it was and I gotta assume from that, that it is supposed to be here on this car.

Stevo: This would be the one on top of the IP. There is not supposed to be anything connected to this nipple? I find this extremely odd.....

Thanks for all the fast replies so far!!!

Your not the first person to think it odd, It does look like it should have a vacuum line on it, but it doesn't.

__________________


1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

the tube is an atmospheric pressure vent.

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What was there thinking behind having it there? Is the nipple there to vent out pressure of some sort? Does anyone know the actual function/purpose of this "vacuum box"?

Whunter: Thanks!! That clears things up alot. So, I was on the right track -it is for mixture adjustment for adjusting the mixture for altitude.

Thanks everyone for being so helpful!!!