I have done numerous searches and reads on this wonderfull forum on the famed diesel engine shut off woes. My 1984 300SD is/was not shuting down when I removed the key. I have the a new vacuum shut off valve but do not want to install it until I am sure that is the cause.

Automatic door locks work, heat works.

Pulled a mity vac directly to the shut off valve next to the IP and it shuts the engine off.

I have cleaned vacuum conectors, tee pee conector, vacuum lines looking for leaks. Not much improvement. Pulled instrument cluster and the ignition key shut off valve and vacuum lines have black oil on it-semi cleaned. Not much improvement.

Tightened the nuts on the big lines with a 19mm wrench going from the IP and now the engine shuts off, but not perfect.

Questions-Do i need to remove/complete clean or replace the ignition key shut off valve? Do I need to replace the vacuum shut off valve next to the IP? Where is this black oil on the key shut off valve comming from? brake booster? worn diaphram in the vacuum shut off valve? There is no oil in the line comming from the shut off valve to the control valve.

Thanks for the help

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1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

609 Certification

Oil in the vacume lines is a sign your vacume pump is in dire need of a rebuild.

Or that it was at some point in its life, and the lines were not cleaned afterwards.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Please nooooooooooo boneheadoc!!! not the vacuum pump! The expensive thing on the front of the engine? Why is oil not in any other vacuum lines except the two near the steering lock? Could it be a bad diaphram in the shut off valve next to the injection pump letting oil/fuel through?

__________________
1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

609 Certification

since door locks and stuff works I doubt the pump is bad. Thats how oil usually makes its way into the vacume lines. it could have been that for 5 years for all you know. I don't know if the shutoff valve could do it. Never had one off. But Its not beyond the realm of possibility I guess.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Oil in the key switch doesn't come from a faulty vacuum pump, it comes from a faulty shutoff device. The diaphram rips and the vacuum system sucks in oil from the injection pump. If the line from the shutoff to the key switch is clear, then it happened sometime in the past and the shutoff device was replaced.

The problem is that the oil ruins the rubber connectors and rubber parts inside the key switch. If you're lucky, it's just a connector. If not, then you'll need to replace that portion of the key switch.

BTW, your door locks are run from a separate vacuum pump (electric) in the trunk.

__________________
Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References

I didn't know the 126 chassis had the electric pump for the doors.THe W116 is the only model I know well.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche