With the engine slowing a little, or stuttering with a good vacuum pull on the shut off valve, you have a failed vacuum valve.
Gets sort of ridicuous when you have to open the hood to shut her down everytime doesn't it?
I think I set the idle so slow I could then kill the engine by leaving it in gear and turning the wheel so as to lug it down until it would just die.
Much easier to just get that valve replaced.

As pointed out earlier, a faulty shut off diaphragm can leak oil into the shut off line and cause havoc.

I placed this small filter in line with the shut-off vac line (brown with a blue stripe on my 1983 300SD) and check it weekly for signs of oil. It has already saved me once - when I saw it was black I checked the shut-off valve and it would not hold a vac. Replaced the valve - make sure you know how to hook it in there or you will get the runaway-red-glowing-bang-big$ engine result.

Being cheap, I flushed the blackened filter with carb cleaner and reused it. Here it is.

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Yep, it's been 2 days, when I do errands, I just leave the car on but locked. I'll bring it to my mechanic on Mon. I'm getting tired of popping the hood.

Sure see a lot of postings relative to the vacuum leaks and having to open the hood to shut off the engine when the components of this unnecessary system fail. Still think that the old "gorilla knob" from the 220D/8's and earlier was the most sensible way to control fuel shut-off. So, big deal if it does not shut off with the key......Its a Diesel, it is and should be different!!! Guarantee you that I never had to open the hood to shut off the old '68.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150

Sure enough, my mechanic installed the shut off valve and it shuts off. He says it will take a few days and it will work better as the leftover oil is purged from the lines, although I could clean the lines to the key switch to help it along. Thank goodness, my wife gets back today and I can't see her popping the hood when she wants to kill it.

Well it shut off for a couple of days and now I have the damn recurring problem! Annoying as hell. I gather that there is also a valve at the ignition where the 2 wires go into that is part of the shut-off mechanism and can be replaced. Has anyone changed this valve and have any tips? The shut -off valve at the IP cost my indy $112 from the local MB dealer and he charge me $38 in labor for a total of $150. I don't want to pay $150 again as I can get this new valve for $20 or so, mail order. Any insights? I guess I'll first try to clean it like can-do suggest before I replace it.

Lycoming- 8,

I had to lift the hood to shut off my old 190D when the cable to injection pump rubber mounts broke.

P E H

edge, that's probably because of oil that has now made it up to the key switch and is clogging the shutoff valve there. I've never had one of these apart, so can't advise on difficulty, but it would seem as though you could just clean it out. On my 240, the shutoff won't always work, and sometimes if I turn the key ever so slightly back toward "on", then it will find the right spot and shut off. You might want to try that, although the wife probably won't put up with that for long.

I'm going to the stealership today to order a new keyswitch (mine has other issues), so when it comes in and I do this job I'll be able to provide more info.

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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

Rick, I stuck a plastic toothpick in the ignition shut off valve and used some lithium grease, no luck. Funny thing is that when I was messing with this switch the last couple of days, it would work for a short time. I am going to try some carburator cleaner this afternoon. If that doesn't work, I am going to buy a new valve. The damnest thing is that I've got the car running smooth as silk with great acceleration but the damn thing won't shut off. My wife calls it a jalopy now and wants a new car.

Rick, you're right...I took too long to replace the vacuum valve at the IP (while having shut off problems intermitently for 6 months) that the oil in the lines fouled the vacuum valve at the ignition switch. After replacing this valve, which is a bear due to the close quarters behind the instrument panel, the engine finally shuts down. It took me 2 hours of trying to get a tiny screwdriver or a ratchet with a scredriver head in there to no avail, no room! I caled my indy who said he couldn't do it today but that it was a bear to remove unless you had tiny hands. I was trying to loosen the ignition mechanism and rotate it to get access to the screws or even removing the dash but I couldn't figure how to. I finally went to Sears hardware and picked up a small spinning thread gizmo that could hold a screwdriver head to get the damn valve out! Finally, it shuts down to give me peace of mind. Now the wife doesn't get a new car and I save $600 per month in this wretched economy. Thanks to everyone for helping me get my sanity back.

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85 300CD Signal Red/Tan sold
83 300D Manganese Brown 109K
97 E420 Midnight Blue 197K sold
98 BMW 328i Vert White 100K, sold
95 BMW 525i White 125K, sold
93 BMW 525iT Red 193K, sold
95 E320 Green Wagon 125K, sold
94 E320 White 127K, sold
85 300SD 156K Grey (Annie), sold
84 300D Lapis Blue 170K (Judy), sold
99 ML 320 Black (lease), 1998 C230 White (lease)
00 Honda S2000 Red (lease)
86 Mercedes 300E (sold)
84 Porsche 911 Red (sold), 1965 Porsche 911 White (sold)

I have this problem at present There is some sign of black oil in the filter and using the Mity Vac, it will not hold vacuum. In my 84 300DT, it appears that there are four bolts that holds the Shutoff Valve, my question is, how do you re & re it? There is not much room between the Shut Off valve and the Oil Filter cannister.

Thank you for your time.

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I forget if there are allen head bolts or phillips head bolts holding the shut off valve in place. Either way, you are right, not much space behind there. You will need a real short tool or an offset tool for the job. Maybe you don't have a real short tool in you kit? They are readily available. I believe there are two paper gaskets and a metal ring gasket. Buy new paper gaskets with the new valve. Be sure to note the order in which they are installed. It might be "paper-metal-paper" but I don't recall. Also be careful of your plastic fittings on other valves and hoses like the one that is at the very bottom of your photo. That runs from the vacuum pump to the brake booster I believe. Those small connections can be brittle and break (where there are smaller rubber hoses leading off it). This can cause problems in the performance of your automatic transmission. When I first got my '82 240D, the auto transmission was acting awful and then as an aside, I replaced the long heavy (non flexible) line from the pump to the booster just because someone had jury rigged one of the tabs after it broke off. When I replaced that main hose, the transmission shifted normally (but I digress). One more thing, look in the manual or on this forum for the caveats of how to put the shut off valve back in. The long shaft you will see when you remove it needs to hook onto something on the inside or else the engine will run away (reportedly) and you won't be able to shut it off. You do it by "feel" more than anything since you can't see what you're doing. You can feel if it's engaged correctly by pulling back on the body of the valve. There is a notch (if I recall) at the end of the rod so it stays engaged. The rod is spring loaded (or maybe diaphragm loaded), so it makes it easier to feel whether or not you have it in place when you sort of pull back on the valve. Then just tighten the bolts and you're done.

Good luck,
Jeff

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- Jeff

1957 W121 190 (history)
1966 W108 250S
1967 W108 250S (parts)
1982 W123 240D (history)
1989 W124 260E

The 4 bolts holding the shut-off valve in place are 10mm. I replaced mine using a normal 10mm box wrench and a short 12 point 10mm 1/4 drive ratchet. Luckily, once I broke the bolts free they could be turned by my finger tips.
Before you take this valve out, as you know, you must first take off the transmission vacuum valve on top of it that varies the vacuum going to the tranny based on throttle position. This is the one that uses two allen boolts, of 6mm I believe.
Have fun,
Adam Bush

Adam:

As you suggest to remove vacuum valve for the tranny, is there anything that I should be watching/noting/marking so as it does not alter the adjustment during reinstall?

Thanks.

The adjustment for the vacuum valve on the IP shouldn't be affected. When you loosen the two allen bolts, you can lift it up about an inch and see how the throttle linkage fits. After this, I would just use a long screwdriver and pop off the ball joint style connector down at the lowest portion of the rod connecting to the vacuum valve. This joint is connected to a lever on the IP. When yo re-assemble, you can use two long screw drivers to reconnect. This is a good idea to do because it's likely this joint needs lubricating anyway.
Good luck,
Adam