Hi, I am recently having trouble with my 83 300D not turning off when your turn the ignition off. I have a 76 Euro to test/compare with and I just have a few questions that I have not been able to find on the forum. First off I read that if the turn off valve does not hold a vacuum that it is bad. The turn off valve does not hold a vacuum but if I apply a vac on it via a mighty vac it turns off. Do I need to replace this valve? It will turn off if I apply a vac to the brown line going into the car or dirrectly to the turn off valve so I think the switch is OK. I think the problem is a bad vac pump. On my 76 I'm getting around 22.5 in Hg. and on the problematic 83 Im getting 4-8 in Hg. I have checked all of the lines to make sure there are no leaks however the line going to the ignition is open when the car is running. Is this normal? Another question I have is: I think the yellow goes to the door locking system? I know the brown is for the turn off. What is the green vac line? OK thanks for the help, Alex

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'76 300D Euro Model 4sp Manual 108k
'83 300D 4sp Manual Conversion

Green is for HVAC controls. Here's a link to some information on the vac system.
http://www.dieselgiant.com/mercedesvacuumtroubleshooting.htm

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'98 E300 DT
'87 190D 2.5 turbo RIP
'92 S500 Sold
'03 3.2TL-S A-Spec

I would disconnect the large Vacuum line at the Vacuum Pump itself and test the Vacuum output there. If you are still getting 4-8 in Hg the problem is in the Vacuum pump.

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84 300D, 82 Volvo 244Gl Diesel

If pump is too weak doesn one have to do manual shutoff every time or is there a way around this,also would brakes be affected?

No vacuum pump = no vacuum assisted brakes

To shut off you can run a vacuum line into the cab and suck on it when you want to shut down, most find it easier to replace the shut off switch

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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"