engine won't stop

my wife was driving the car the other day, a 84' 300cd when she got home the engine wouldn't stop running after she had turned and removed the key. after a few minutes, not knowing what to do, she put the key back in. backed the car into the driveway and then moved it forward again into the garage and tried again. this time the engine turned off. i noticed the other day when i was starting the car that the key would not turn at all, i removed the key and then successfully turned it to start the engine. i have also noticed that sometimes when locking the car the passenger side door is very slow to lock (5-10seconds) or that it won't lock at all. this car is new to me, but i suspect it a vacumn related problem or a key problem? i would like to fix this problem myself and would very much appreciate the help from the forum members.

[JimSmith]

mark300cd,
This is a very common problem and you will find a wealth of hints, instructions and recommended tooling to fix your vacuum system by doing a search on the subject. You have correctly surmised the vacuum system is the culprit. Now you have to isolate the problem and repair the leak. The engine is supposed to be shut off using vacuum, however, when the vacuum system is faulty you can use a handle provided for this purpose on the injection pump. It is less convenient than using the key, but it works. Just lift the hood and look toward the rear of the injection pump. I believe it has a red decal on it that says "Stop" or something like that. Good luck. Jim

[Palangi]

First place to look for that vacuum leak is the rat nest of vacuum connections above the oil filter. These are easily dislodged during an oil change. Hopefully you will get lucky and find it there. Otherwise it's likely to be in the doors or under the dashboard. Sometimes to can hear a leak if you listen closely.

[Aaron]

If the one door is slow to lock, there are some tests you can perform before even tearing anything apart..

1. Sit in the car, engine off, doors unlocked. Push driver's plunger down and listen to both doors for any hissing noises. You will most likely find it in the door that is slow to lock.

2. With engine running, press driver's lock plunger down and see if it still takes a long time for the other door to lock.

You can remove both door panels and put a vacuum gauge on the elements in the doors and check if either one of those is the source of the leak. The yellow/green line is the unlock side, the yellow/red line is the lock side. In the meantime, if you don't want to diagnose the source of the leak yourself, you can just pop the hood and disable the entire central locking system by plugging the yellow/green and yellow/red lines back by the firewall, where they come out atop the oil filter housing.

The emergency shutoff lever under the hood will look right at you if you're standing on the driver's side of the car looking at the valve cover. It's a piece of throttle linkage with a red label on it marked "STOP". Turn the key off, pop the hood and push this linkage towards the valve cover to kill the engine.

[MVK]

I second the opinion of Palangi. I have had this problem after my very first oil change and it scared the day lights out of me. One of the plastic vac tube had gotten loose from the rubber connector. I replaced all the rubber connectors and all works fine again.

Hope this helps. Keep us posted.

MVK

thanks for everyones help. Aaron, i tried the things you suggested. the results are as follows:
1. when i sit in the car with the engine off (has not run for over a day) and i lock the drivers door, the paasenger door remains unlocked.
2. i then started the engine and waited a couple of minutes and then locked the drivers door, the passenger door remained unlocked.
3. i then drove for 5 minutes with the drivers door locked, the passenger door remained unlocked. when i drove for 5 minutes with the drivers door unlocked, and then locked the drivers door the passenger door would then lock.
4. after driving for 5 minutes, with the engine just shut off, using the key the drivers door, passenger door, and truck locked. the fuel door remained unlock.

i just bought a mity vacumn tester, though i haven't learned to use it yet. what does all this mean and what should i try next. thanks again for the help.

[slowmoe]

Great! Now drive the car for for 2 minutes north then 3 minutes south.

Wiggle your toes, scratch your ass and say, "Vacuum, Vacuum, Vacuum" three times fast...Your problems will be solved.

[slowmoe]

Just kidding Mark.

You are on the right track. I know vacuum problems can be a bear to track down. I just replaced the vacuum pump, a window actuator and the shut off valve on my 124.

Rest assured that those more knowledgabe than I on the 123 will lead you in the right direction.

Welcome to the forum.

Sounds like you have a good old case of vacuum leak-itis. It plagues these cars because they live older than the rubber hoses do. DO a search on vacuum leaks in this forum there is tons of info on it. My car done the same thing to me except a tee fitting had broke of the main vac line even the emergency stop didn't work. So against my better judgement i was told to cut my fuel line. (chokeing it out at the breather didnt' work either). Hope this helps ya out a little. Any problems send me a message i'd be glad to help.

[1stimer]

This is all brand new to me, but I somehow just fixed a long shut off on my new diesel.

You need to purchase a vaccum pump like a mityvac. I got mine from sears for less than 30 dollars.

Just plug the tubing from the mityvac into different connectors. It should keep the pressure on the mityvac, if it doesn't then it is cracked or leaking somehow.

I replaced one of my connectors that wasn't holding a vaccum with a connector that came with the mityvac. The car shuts off in less than a second now. I still have some vaccum problems....I have a golf tee in one connector and a loose line that is supposed to go into it. I need some more connectors as mine seem pretty brittle.

You might just go in there, poke around, and see what you find. Loose lines, brittle conectors, etc.

I also poked around under drivers seat....I think thats the places...1. by firewall 2. under drivers side 3. in doors

please let me know if I'm way off base with any of this guys.

Another place to look for leaks on a coupe is in the seat latch, this is the blue vacuum line.

[1stimer]

Thanks 123-----I did not even see he has a coupe. I'm not sure of the differences between the coupe and sedan as far as vaccum goes.

i havce seen the blue line under the seat, what is this for? can i disconnect it at the seat end of the line and check for a vac leak?

First thing to check is that the latches work on the seat back, if they don't work then start checking for leaks. Most likely the leak in the seats would be coming from the diaphram under the seats, so check this first.

i am making some progress. did vac tests in various places and got the fuel door working. it don't think it was leaking but the probe was gummed up in the guide. the system seems to be working, now when i start the engine all the locks work together...which it didn't do before. if i let the car sit a few hours the locks still work together without having to start the engine. i think i have a leak in the blue line going to the seat backs, but i'm not sure. i assume that the system is to lock the seats when the engine is running unless you puch the small black button on the side of the seat? the line does not hold a vac at the firewall. it seems hard to get at under the seats, do you guys just unbolt the seat? thanks again!