1979 300D Wont Turn off when key is in the off position. - PeachParts Mercedes-Benz Forum

OPT652 · #1 07-10-2005, 02:41 PM

Hello All,

I just bought a 1979 300D. The only problem is that when I turn the key to the off position, and even take the key out! The car will not turn off. To get it to turn off, I have to pop the hood. Then take a small rubber hose from the main vacuum line and attach it to where the line from the ignition switch was, to get it to shut off. Forgive me for being general, this is my first benz and I am still learning. One other note, the guy that I bought it from said this had just started happening, it wasnt a constant problem. One thing I noticed is when I blew into the line coming out of the ignition switch, I heard a bubbling sound, could this be a problem?

I appreciate any help.

Kevin Meyn

TX76513 · #2 07-10-2005, 02:50 PM

I am not real familiar with a 79 300D do you have a lever in your engine bay that says "Stop"? That could save you the trouble of pulling lines till you fix. Do you have a miti-vac if not you are going to need one for your car to check vacum (its an inexpensive got-to-have tool). Commonly the shut off valve goes bad that's what I would check first, then the shut off valve at ignition

Joe Bauers · #3 07-10-2005, 02:56 PM

You have a vacuum problem, in all likelihood. Do the vacuum door locks work? Does the power braking work properly? You need to search out the vacuum system to find out what's going on. It could be a leak in the door lock circuit, a leak at the injector pump with the vacuum shutoff, a faulty vacuum pump. If it turns out that you need to replace the vacuum shutoff at the pump, have someone who knows what he's doing it install it. Installing it incorrectly can cause the engine to run to its death. Do a search, and I'm sure you'll have loads of ideas.

Joe B.

OPT652 · #4 07-10-2005, 03:12 PM

The Vacuum door locks do not work, and the braking is fine. What is a miti-vac and where can I find one? Another thing when I use the method I talked about to turn the car off. When I pull off the hose after the engine is shut off, there is vacuum pressure and it makes a little poping sound when you take it off because the air is being released. But when I take off the line that is originally connected to the engine from the ignition switch, it doesnt make that sound and there is no air, could there be leak in this line? By the way what are these parts called that I am describing?

Kevin Meyn

mikemover · #5 07-10-2005, 03:23 PM

Quote:

Originally Posted by OPT652

Hello All,

I just bought a 1979 300D. The only problem is that when I turn the key to the off position, and even take the key out! The car will not turn off. To get it to turn off, I have to pop the hood. Then take a small rubber hose from the main vacuum line and attach it to where the line from the ignition switch was, to get it to shut off. Forgive me for being general, this is my first benz and I am still learning. One other note, the guy that I bought it from said this had just started happening, it wasnt a constant problem. One thing I noticed is when I blew into the line coming out of the ignition switch, I heard a bubbling sound, could this be a problem?

I appreciate any help.

Kevin Meyn

As the previous post says, use the little red "stop" lever, attached to the throttle linkage near the valve cover. This will reliably stop the engine.

You have a bad vacuum leak that is causing this problem. Unlike a gas engine, which is shut off by cutting off the electrical supply, a diesel must be shut off by stopping the fuel supply. This is done with a vacuum valve on the injection pump.

The most likely things to be leaking vacuum are your automatic locks, or the vacuum shutoff valve itself. Look at the vacuum lines in the area near the brake master cylinder/vacuum booster. Find the line that leads to the locking system (I think it is the yellow hard plastic line...or perhaps yellow with a green or blue stripe?...I forget), disconnect it and block off the now-open line coming from the engine. If the problem persists, then you probably need a new vacuum shutoff valve. It's the white/beige-colored plastic thing on the back end of the injection pump.

Mike

whunter · #6 07-10-2005, 03:25 PM

Quote:

Originally Posted by OPT652

Hello All,
I just bought a 1979 300D.
One thing I noticed is when I blew into the line coming out of the ignition switch, I heard a bubbling sound, could this be a problem?
Kevin Meyn

The bubbles are engine oil sucked through the shutoff valve.

Replace your injection pump shutoff valve, and blow out the tube from start switch to shutoff valve with brake cleaner, followed by air.

Read this thread before you try to DIY the shutoff valve R&R.
http://www.peachparts.com/shopforum/showthread.php?p=824840#post824840

Here is a thread with many links you may need later.
http://www.peachparts.com/shopforum/diesel-discussion/102268-name-these-parts-help-new-members.html#post699016

OPT652 · #7 07-10-2005, 04:09 PM

Is my 1979 300D supposed to have this? http://www.peachparts.com/shopforum/attachments/diesel-discussion/20597-name-these-parts-help-new-members-name_this-_part_2.jpg

mikemover · #8 07-10-2005, 04:14 PM

Quote:

Originally Posted by OPT652

Is my 1979 300D supposed to have this? http://www.peachparts.com/shopforum/attachment.php?attachmentid=20597

Yes, that's the ALDA. Yours may look a little different. Mine doesn't look exactly like that one either. It affects turbo boost, and should not be part of the problems you're describing. It is adjustable, but I woundn't advise doing so if you don't know what you're doing with it. The vacuum shutoff valve we're talking about is on the back end of the injection pump, right BEHIND the ALDA.

Mike

OPT652 · #9 07-10-2005, 05:39 PM

How can I replace this Shutoff valve? Is it a real pain? And when you say behind are you talking to the right of the ALDA where the line from the ignition switch attaches? Is that where the shutoff valve is?

Kevin Meyn

OPT652 · #10 07-10-2005, 06:57 PM

Alright I took out the shutoff valve and was covered in oil. But I depressed the end of it and put my finger over the hole and it held, therefore creating a vacuum right? Do I need a new one still? It wasnt stuck at all.

Kevin Meyn

mikemover · #11 07-10-2005, 07:02 PM

Quote:

Originally Posted by OPT652

How can I replace this Shutoff valve? Is it a real pain? And when you say behind are you talking to the right of the ALDA where the line from the ignition switch attaches? Is that where the shutoff valve is?

Kevin Meyn

Yes, that's it.

VERY IMPORTANT!

DO NOT start your car with the shutoff valve removed!!! Also, if you install a new one, or re-install that one, make SURE it's hooked up inside the pump just like it was when you took it off!!! The engine can "run away", far beyond the RPM limits of the engine, and there will be nothing you can do about it.... causing much destruction and possibly injury to you. Be careful.

I don't think the "finger test" you did is a reliable indicator one way or the other. Did you test for leaking vacuum locks before you removed the valve? You said earlier that the locks don't work at all....do they work at all when the engine is running?....If not, then that means either they are disconnected already, or there is a significant leak in them.

REMEMBER, don't start the engine without that shutoff properly installed!

Mike

J. R. B. · #12 07-10-2005, 10:04 PM

Quote:

Originally Posted by OPT652

How can I replace this Shutoff valve? Is it a real pain? And when you say behind are you talking to the right of the ALDA where the line from the ignition switch attaches? Is that where the shutoff valve is?

Kevin Meyn

For God's sake listen to WHunter. Read all of WHunters links and when you think you have everything memorized read them again before you do the job. When WHunter and the rest of these guys speak everybody listens.

mikemover · #13 07-10-2005, 10:09 PM

Quote:

Originally Posted by J. R. B.

For God's sake listen to WHunter. Read all of WHunters links and when you think you have everything memorized read them again before you do the job. When WHunter and the rest of these guys speak everybody listens.

Yep. WHunter is ALWAYS on top of this stuff. Check out the stuff he linked to.... This is not really a difficult or expensive problem to fix.... Just a little tedious.

Mike

OPT652 · #14 07-11-2005, 12:20 PM

Quote:

Originally Posted by mikemover

As the previous post says, use the little red "stop" lever, attached to the throttle linkage near the valve cover. This will reliably stop the engine.

You have a bad vacuum leak that is causing this problem. Unlike a gas engine, which is shut off by cutting off the electrical supply, a diesel must be shut off by stopping the fuel supply. This is done with a vacuum valve on the injection pump.

The most likely things to be leaking vacuum are your automatic locks, or the vacuum shutoff valve itself. Look at the vacuum lines in the area near the brake master cylinder/vacuum booster. Find the line that leads to the locking system (I think it is the yellow hard plastic line...or perhaps yellow with a green or blue stripe?...I forget), disconnect it and block off the now-open line coming from the engine. If the problem persists, then you probably need a new vacuum shutoff valve. It's the white/beige-colored plastic thing on the back end of the injection pump.

Mike

Mike,

I looked at the vacuum lines and I noticed that the rubber fittings around the vacuum lines are a bit big, there is some space around the vacuum hose with the rubber hose fitting over it. Is this the leak? Also I have the locks and the rest of the vacuum lines going through one way valves? (All the lines except for the one going to the shutoff valve) Is this unusual? Could this be the problem?

P.S. When I turned the car on and tried the locks, it still didnt work. Only the drivers side went up.

I appreciate all of your help.

Kevin Meyn

mikemover · #15 07-11-2005, 01:46 PM

Quote:

Originally Posted by OPT652

Mike,

I looked at the vacuum lines and I noticed that the rubber fittings around the vacuum lines are a bit big, there is some space around the vacuum hose with the rubber hose fitting over it. Is this the leak? Also I have the locks and the rest of the vacuum lines going through one way valves? (All the lines except for the one going to the shutoff valve) Is this unusual? Could this be the problem?

P.S. When I turned the car on and tried the locks, it still didnt work. Only the drivers side went up.

I appreciate all of your help.

Kevin Meyn

If those rubber t-fittings and x-fittings are old, dried, and stretched, then they are probably at least a part of the problem. I'd replace all of them. The check valves are supposed to be there. If you remove those, be sure to put them back just like they were, not backwards.

If the rubber under the hood has been neglected, then the rubber vacuum elements inside the doors are probably shot as well.

Mike

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