83 300d will only shut off if I lock the doors - PeachParts Mercedes-Benz Forum

biobenz240d · #1 01-14-2007, 07:51 PM

My 83 will only shut off when I lock the doors. When I turn off the key the idle slows down but won't shut down till I lock the doors. Is the problem in the lock vac system or in the shut off valve it self ?

thanks in advance.

kerry · #2 01-14-2007, 07:56 PM

Probably the lock system. You'll need a Mity Vac if you don't have one already. Quickest test is plug the vacuum hose going to the door locks under the hood and see if the shut off works ok. I think the hose to be plugged is the yellow one. Someone else can confirm that.
Once you've determined it's the doors and not the shut off you can chase down the exact leak with a Mity Vac. The pods themselves fail and I've found the hose cracks where it goes into the driver's door where it gets more flexing than anywhere else.

biobenz240d · #3 01-14-2007, 08:04 PM

I have a mity vac and went out today to try and diagnose the problem but after 5 minutes it started with the freezing rain. My garage is full of biodiesel stuff so I'll have to wait for better weather.

JimmyL · #4 01-14-2007, 08:07 PM

Kerry is leading you in the right direction. My wagon won't shutoff if I try to turn it off with the temp wheel on "heat". I guess one of the vac pods used for heat only has a leak....

biobenz240d · #5 01-14-2007, 08:13 PM

I kind of like it that I can pull the keys out and still have it running so I can move another vehicle with the same keys. don't drive the benz with the keys out , don't ask me how I know that

kerry · #6 01-14-2007, 08:22 PM

Much of the door lock system can be tested by accessing the lines under the driver's floormat.

rg2098 · #7 01-15-2007, 05:14 AM

The door lock circuit is quite simple. There is a supply line that goes into the drivers door and a switch that applies the vacuum to either the unlock or lock circuits. I believe green lines are un-lock, and red are lock. You have a leak in the unlock circuit. It could be a junction, or at a door pod.

Samuel M. Ross · #8 01-16-2007, 09:19 PM

Quote:

Originally Posted by rg2098

The door lock circuit is quite simple. There is a supply line that goes into the drivers door and a switch that applies the vacuum to either the unlock or lock circuits. I believe green lines are un-lock, and red are lock. You have a leak in the unlock circuit. It could be a junction, or at a door pod.

... it is relatively simple but I found a diagram very helpful... but when they turned out to be in black & white I found them difficult to read. So after I finished my door-lock repair project I created a color coded diagram for the W123 chassis door-lock system. See it at:
http://www.peachparts.com/shopforum/showthread.php?t=160169
Yes, you should be able to access much of the various [many] lines under the two front floorboard mats. From your symptom, there appears to be a heavy leak in the door-open circuit and so when you lock the doors, this action closes off the leak which is in the other half of the door-open/lock system. The diagram which is in MS Word format should help! Print it out on a color printer and you should be able to read all of the text as well as easily trace the different lines
Regards,

maddogg20 · #9 01-16-2007, 11:22 PM

Whats up.

I also have an 83 300d. My car was doing the same thing, just running, until i locked the doors, and then itdd shut off. it got to the point where the car wouldnt shut off at all due to the vacuum leaks, SO I started to trouble shoot my vac system. Under the hood you have 2 yellow lines that control the body locking system. One of them is the supply to the vacuum resorvoir in the trunk, and the other supplies the locks. The one with the blue stripe is the lock circuit supply im pretty sure, but it may be the solid one. Neither the less, I found a leak in the front pass door and the trunk element, and replaced them but I'm still having issues, but those are because I have a leaky IP shutoff valve. To test the IP shut off valve simply, remove the line going to it, and stick your mighty vac hose onto it and apply vacuum, it should hold it. If that tests good, then move on to the doors. The best way for you to test them is to get at their control lines and isolate them. The junction for the lines that control the pass doors, trunk and gas door is right under the floor mat on the pass side right by the door jamb under a black plastic cover. The drivers side door junction is in the same place on the drivers side. Basicially, all U have to do is stick a piece of rubber hose on ur mighty vac and disconnect eash element 1 at a time, checking the unlock (yellow with green stripe) hose with ur mighty vac, and the lock (yellow with red stripe) hose. Just pump the vac and wait like 20 secs and see if it holds it. If it does then that elements good. If not, then you will have to take the door panel, or whatever panel covers the element and then check it again. Keep in mine that you will also need to cap and test the lock and unlock lines that cross over from the drivers side to the pass side, and cap the vacuum supply line in the drivers door that goes to the master vacuum switch, and then hook ur mighty vac up to that line under the hood because there is a check valve in the line and if u test it from inside the car itll look like theres a restirction in it, when there really isnt.

If you think you have fixed all the leaks, you can test each function of the elements. just unplug the 2 lines, one at a time from the master vacuum switch inside the drivers door and mighty vac each one and if they hold vacuum, then that side of the circuits is fine. This way, if your cars still acting up, you can rule out vacuum leaks in the locking circuit as a problem.

IMPORTANT NOTE:
When you are in the doors or trunk, have some rubber vacuum caps handy so you can cap the lines to the element and test the plastic lines them selves. I had a bad element in the pass door as well as the unlock line to the pass door being cracked right where it goes from the car itself into the door. So be sure to check all your lines by isolating them, and while your in there replace the little rubber connectors that go from the plastic tubes to the element, itll save u a headache down the road.

I hope this was helpful.