Won't shut off - vacuum problem?

[mbzr4ever]

Hi guys,

This is for my 79 240D I'm restoring....

I just replaced 3 of the remaining glow plugs last night. I was so proud she started up right away, and sounded rather good.

But today, I started her up and darn if the engine did not shut off when I turned the ignition off. So I went to the red STOP lever under the hood, pushed it and it stumbled off and quit.

Then I went to the post office about 2 miles from here. It sounded like she was revving faster than normal. Again, the engine did not quit when I turned the key off.

This time, the engine did not stop after pushing the STOP lever several times. It was scarey, but finally it turned off, after pushing the lever for about about a minute or so. And embarassing.

Then I go straight home and turn the engine off. And it does not quit, even after pushing the STOP lever several times. Then I remember reading about blocking the air intake, so I got a brick and covered the hole. It sorta worked but still did not shut off. Then I got the idea of covering the hole with the brick, and pushing the STOP lever at the same time. That worked, and the engine died.

OK, so some weird things I noticed the past week or so:

1) Door locks were not working properly, some would not unlock.

2) The pedal for the acceleration felt like it was sticking in an open position, in other words, the car would go rather fast without my pushing on the pedal much.

3) Please don't tell me I screwed something up with my GP installation to cause these problems...Or please do, maybe it is something that I can fix or redo. In light of items 1 and 2 above, however, I don't think the GPs are the issue.


Thanks everyone.

[bustedbenz]

First guess? In wrenching on the glow plug job, you inadvertently snapped a brittle 20+ year old vacuum line.

[kerry]

Combination of problems? Disconnected vacuum and a sticky accelerator linkage??

[mbzr4ever]

Now that you mention it, there is a rod (connects to the STOP button)
that was quite difficult to work around the 3rd GP (#4 being closest to the firewall). It is right in the way and I remember having to fiddle with it up/down/around to change #3 GP.

Will check again under the hood for anything obvious, like the cracked vacuum line, but WDIK?

Learning fast, though...

Edited to add:

Quick check at the vacuum lines, the black ones look new. Just had the car worked on for timing chain replacement and injector work, I think they replaced the lines at that time. Don't know for sure until I find the receipt....

Found receipt of 6/07 - only mention of new vacuum pump gasket.

Only other receipt of vacuum work done was in 7/02, where they replaced the trunk lock element. They also wrote they changed the vacuum y fittings, nylon line and connectors, maybe this is just for the trunk area? No charge for the fittings/lines/connectors, receipt kinda hard to read....

[Diesel Dan]

I think your no shutoff problem is almost certainly vacuum related. Keep checking vacuum connections. If you fail to find a loose or disconnected or brittle line, then get a mityvac vacuum tester and start pressurizing stuff and watch the guage to see if it's holding the pressure.

[Biodiesel300TD]

For the sticky throttle. Clean and lube all the ball joints on the linkages. They get dirty and gritty which makes them stiff and sticky.

The shut off issues is likely a vacuum leak. Look carefully around the engine bay, following each vac line, make sure they are all hooked up. It sounds like you either pulled one loose while changing glow plugs or broke one of the connections.

[kybenz]

to the part about the shutoff not working, i had a similar prob, it was suggested to me that one of the linkage rods that goes down behind the inj pump needed to be adjusted. I did that (shortened i think) and it would kill properly. Mine is an 84, don't know if the setup is the same.

[Sbean]

My '80 300 TD needs to have the idle adjustment knob on the dashboard turned all the way down before the stop lever will work. Steve

[komaiaboyz]

Hi I just inherited my mom's 1984 300D Turbo. It had been sitting in her driveway since she got a wagon, with my dad driving it perhaps once a month. The issue with it is when I turn the key for it to shut off, it runs for perhaps 30 more seconds and then sputters off. My son noticed that the area in which you put the key in, got hot one time last month, but since then it hasn't gotten hot, so I am thinking it has something to do with the key? Any suggestions? Thanks in advance, I've tried the search, and now I've discovered more things that I need to do to the car.

[mbzr4ever]

Originally Posted by Sbean

My '80 300 TD needs to have the idle adjustment knob on the dashboard turned all the way down before the stop lever will work. Steve

Is that all the way to the right or left?

[toomany MBZ]

Originally Posted by komaiaboyz

Hi I just inherited my mom's 1984 300D Turbo. It had been sitting in her driveway since she got a wagon, with my dad driving it perhaps once a month. The issue with it is when I turn the key for it to shut off, it runs for perhaps 30 more seconds and then sputters off. My son noticed that the area in which you put the key in, got hot one time last month, but since then it hasn't gotten hot, so I am thinking it has something to do with the key? Any suggestions? Thanks in advance, I've tried the search, and now I've discovered more things that I need to do to the car.

There is a vac line going to the ignition switch, don't know how anything would get hot in that area. Sounds like you have a vac leak somewhere. One of my cars had a similar problem, I removed the door locks from the system, (plugged off the yellow check valve near firewall) and the car shut off with the key, no problem. On my current SD, I have a delay in shutting off, no stuttering, so far I can live with it.
mbz4ever, should be all the way to the left, or fewer rpm, sounds like you have a vac leak somewhere also. I think only non turbos have that idle adjust on the dash.

[mbzr4ever]

toomany MBZ,

Thank you for your reply, I will try to shut it off again with this idle adjustment on lowest setting.....and my brick to smother the air intake ready, just in case....

Yes, I suspect a vacuum leak also - now all my doors locks are not unlocking as they should. I have made an appointment with the mechanic for this week, as I don't think I can do this myself...I don't have the vacuum test tool (or mityvac, or whatever it is called), and I'm busy with a tune-up for the 300E....sucks when both cars are acting up the same time....

[Stevo]

Find the brown vacuum line that goes to the shut off switch on the rear of the injector pump. With the engine running apply vacuum (suck on it) to that switch, car shuts off=bad vacuum switch, no change= big vacuum leak some place else, most likely door locks. get some golf tees and start by plugging the yellow line by the brake booster thats the one to the locks. See if that cures the problem. A Mity Vac is very handy to trouble shoot the system.

[mbzr4ever]

Stevo, and everyone,

You will never guess what I just found in checking under the hood again....

a hose disconnected from a connector, right around where the Y and yellow and brown lines are!

Put it back together, tested it, and she shut off, doors locked and unlocked like normal.

It was only obvious after I spent the past day or so studying pictures and diagrams of vacuum lines, so I must have accidently disconnected it while I was installing the GPs.

Like this one:

http://www.schumanautomotive.com/forums/showthread.php?t=2755&highlight=vacuum

You don't know how happy I am, I can cancel the appointment with the mechanic!!


Thank you, everyone! I have learned a lot, especially how to shut off the engine in an emergncy, with a brick on the air intake.

[Sbean]

On my '80 300 TDs, turning the idle adjust knob clockwise lowers the idle speed. When increasing the idle speed it's a good idea to "help" by pressing on the accelerator pedal so the idle adjust doesn't have to work so hard against the return spring. Steve