Temporary shut-off fix
 

I am in the process of trying to fix some little irritating problems I inherited on my new 1982 300D Turbo. I seem to have all the most common problems (just my luck).

(# 1 for the day) I have the ever common problem of the car not shutting off with the key. I have determined that I have no leaks in the vacuum (brown with blue stripe) from the injection pump to the key switch.

I have decided that until I find the reason it still won't shut off, I can unplug the vacuum hose from the key switch (brown with blue stripe), and extend that same vacuum hose with another piece of vacuum hose, and let it hang down from below the steering wheel, and now shut off the diesel by sucking on this line from the driver seat. Somewhat embarrassing if people are anywhere near. but at least I don't have to get out and open the hood every time I want to shut down the motor.

So, If I'm right, the solid brown vacuum line should hold vacuum as it enters the key switch and then with the key turned off, it should then transfer over and draw vacuum to the (brown with blue stripe) vacuum hose going to the injector pump, and in-turn shut off the motor?

If I have vacuum going into the switch from the solid brown vacuum line but it's not drawing vacuum on the "out" line (brown with blue stripe) to the injecter pump...The problem is in the switch .... Right? Or could it be that I don't have enough vacuum going into the switch? How much vacuum should there be there?

One clue. The key does not always want to turn on without some finessing (Like you would get with a duplicate key not cut just right) but will always turn off without effort.


One other question. Do the Shop tech's read from this forum, or do I need to post to their forum specifically?

Thanks for any help on this issue.

David Dodge
1982 300D Turbo

I know someone who had problems shutting of their car, so they took some fishing line and attached it to the shut off switch on the engine, and ran it to the outside of the hood. They just pulled on the line when they wanted to shut off the engine. They did this for about a year until they decided to replace the Shut off Valve.

I had the same problem I think. I simply replaced the hose going to the valve. Works fine now. In my case, it must have just been cholesterol in the hose.

Cool fix
 

I read your post to my wife and she told me if I EVER suck on my engine then we are getting a divorce.

JCD

jcd, could you persuade your wife to just... no, never mind...

You need to find the vacuum leak and fix it. Do the door locks work okay? If they don't, pull vacuum at the mess of lines above the oil filter and find the one that won't hold a vacuum, then start down the line until you find the leak.

Most likely the leak will be one of the door lock diaphragms. They cost no more than about $15.

Good luck,

I recently had a run-on problem with my '83 300D. Thanks to tips from the forum, I looked and found oil around the vacuum line coming into the shut off valve. With the help of my wife and instructions that I picked up from the forum, I changed out the vacuum shut down valve. After the replacement, I was still having run-on problems. I discovered that the vacuum hose was not sealing in the rubber adapter that fits on the vacuum valve. A good wrap of electrical tape around the vacuum line and the beast runs great now and shuts down every time.

Thanks to all!!:)

Quick tip
 

Try locking the front door, then shut off the engine. If the engine shut's off, then you probably have a downstream vacuum leak in the locking system.

JCD

I don't have automatic door locks so I guess I'm lucky there.

I did find the mother of all leaks last night before I had to quit. It was (and I don't know what it is called) on the large line that comes off of the booster. All of the vacuum lines originate from this connection. Towards the booster side where it is spliced in, it's white. Then on the other half it has at least one nipple that has broken off and the previous owner had it loosely taped and glued shut (in a failed effort to stick it back on) There must be glue in it because there is absolutly no vacuum coming from what used to be a nipple. There is a small screw in the other opening towards the booster. This thing looks like a device that I will have to order. Does anyone know what it's called and do I have to get this from a MB place. I'm hoping this is the root to all my problems.

I knew someone of questionable mechanical ability owned my 1987 300D previously when I saw a manual choke cable wired up to the stop lever under the hood.

I'd rather solve the vacuum leak with the proper diagnostic tool (Mity Vac) than route a choke cable under the car.........

My 1982 300D had a vacuum hose of the wrong size going to the transmission modulator. It fell off. Previous owner thought it was natural for Mercedes diesels to shift hard as a rock.

:)

300D

David,

ALL 123 cars have vacuum door locks. They work by simply locking the drivers door and all the doors, the trunk and the fuel tank door will lock, providing, of course, that they are working correctly. Since you obviously have a vacuum leak keeping the shut off from working, the same lack of vacuum prevents your door locks from working as well.

jcd's trick for quick and dirty testing is a good one. Lock the drivers door and see if the engine will then shut down. You will have to hook the system back up the way it was before you created the "suck tube" for the test.

Let us know the outcome and we will lead you to the problem. Or drive it to Cedar Hill park in the Dallas area on Novemeber 17 and we will gang up on it and find the problem.

Have a great day,

sounds like the shut off valve is shot probably leaking inside the Injection pump its really hard to tell with the valve still attached
I would recommend changing the valve its a very easy job and if you get the part from www.performancemotorcars.com

it will only cost $33.09 cheapest your going to find I would think next runner up is this site for $10 more I would do a search on shut off valves here and get instructions on replacing. even if its not the cause that valve will go one of these days might as well change it while the parts are cheap
but that is my theory:cool:


Jeff

David Dodge,

As Larry noted you do have the equipment for automatic door locks in your car, but also have a vacuum system leak that has rendered the door locking system non-functional. If you can manually draw a vacuum on the tube going to the shut off valve, and not get a mouth full of engine oil, you are probably not dealing with a bad shut off valve. As Larry noted, you probably have a vacuum system leak in the door system.

I disabled the door lock system on my 1982 240D when I suffered similar symptoms, as the door locks were deemed a less vital function than shutting the engine off. I cannot remember which tubes I plugged but it worked and I have not had another problem since. Since you will likely not miss the system if it continues to be non-functional, you may want to try this. I plugged the lines by screwing a slightly oversized screw into the tube and then covering it all with a few winds of electrical tape.

You might also test the key operated vacuum switch by hooking it all up as it was, and then taking the line that goes back to the vacuum system and routing that to inside of the car. Then, when you turn the key to the off position, you can suck on the line and if the car shuts down, the switch should be healthy.

Good luck, Jim

Alright, you guys really have me thinking now. I was all ready to replace my shut off valve this weekend!!

However, the lock on my passenger side front door does not unlock or lock the rest of the car anymore. And if memory serves, these two issues developed around the same time.

Is there a way of determining wheather or not it is indeed the shut off valve? I know that there is vacume at the line- if I unplug the fitting there is a hiss.

Do I trouble shoot the lock first? Thoughts are appreciated.

1992 300D 2.5 173,000 miles

Unbelieveable.... I have door locks on this car too! The friend that sold it to me didn't know that either I don't think. As you can tell I am a real new guy to mercedes. I like this car more everyday. If I get everything working I'm sure I will be amazed at the quality of my new car. I will solve the vacuum thing if it kills me. Thanks to everyone who has helped.