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1981 300 C D Bot with 14K miles.
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525 Posts
problem

Has anyone had this happen? How do you fix it? 84 300 Turbo Deisel
Have same problem but my car is being fixed as we speak.

There is a leak in your vacuum system which causes your shut off valve not to work. You must check your vacuum system.

There is a manual shut off under the hood, which will shut it down immediately. It is painted red.

Do a search under Key Squishy and you will find a more thorough explanation or you can find it under my previous posts if you click my name. :)
 

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1984 300D
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5,070 Posts
The Manual Shutoff is a Sheet Metal Lever about in the middle of the Valve Cover on the Drivers Side (US cars). Push it towards the Valve Cover to shutoff.

While it is most often a Vacuum leak in the Lock or Climate Control System the Vacuum Shutoff Valve on the Fuel Injection Pump can go bad and there is also a Vacuum Valve on the Steering Colum that can go bad (this is what your key actuates).
Check for disconnected hoses/tubing’s going to the above.

If the effort you need to press on the Brake Pedal has become much harder and braking is scary you need to check the Vacuum Pump also.
 

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1997 Mercedes E420 Sport & 1985 Mercedes 300 DT
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2 Posts
The cable to my hood is broken up under the hood and cannot open my hood. How do I open the hood through the grill to replace the cable and the broken safety hood pull? Please help!!!

Thank you!
 

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'83 300DT 423,000+ mi
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26 Posts
300DT "Dieseling"

Until I fixed the vacuum system, I had to depress the driver's door lock button to have the car shut off as designed. You have a vacuum system leak/problem.
 

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Premium Member
99 SLK230 Kompressor, 5 Speed Manual
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1,117 Posts
Once you get the hood open, the most common cause of no shut off is knocking off the shut off solenoid vac line when changing the oil filter.

Hope this helps.
 

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1983 240D Standard
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24 Posts
I have this problem right now. Not only that, but the red shut off lever wont work either. Twice tonight I had to stop the car by stalling.

In support of English Bulldog and 300Dman, the explanation is most likely a "massive" vacuum leak in the form of a busted vacuum brake booster hose.

That hose is en route to me now. If replacing it doesn't fix the problem, I'll add another reply.
 

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496 Posts
If the red shutoff lever doesn't work - you've got a bigger issue, since it is bypassing the vacuum system.

Dave
 

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'80 300SD (W116), '81 300D, '89 560SL, '01 E320
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140 Posts
Lock the driver's side door a few moments before you turn off the key; then when you shut it off, the engine should stop normally. If this works, then you will, in the short term, want to open the hood (when you can), find the vacuum line that leads to the doors, and cap it before it splits (it goes into a rubber "Y" and then splits off into two yellow/reddish tubes). To figure it out, you can open the hood, while the engine's running and the key is turned off, then pull out the tube and block it with your thumb (the one leading to the motor, not the one leading into the firewall toward the door), and the engine will shut off if you're successful. Cap that tube. Mine's still like this, and I just lock the doors manually. One day I'll fix the leak.
 

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1983 240D Standard
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24 Posts
If the red shutoff lever doesn't work - you've got a bigger issue, since it is bypassing the vacuum system.

Dave
Yes, that's correct. I was confusing the two, as neither worked in my car. But I did fix my vacuum leak, so now I can switch off the car with the key.

I'm assuming my malfunctioning shutoff lever is due to the missing throttle plate inside the intake, possible removed when a previous owner disabled the EGR, as they broke (or didn't bother to repair) that last bit of linkage.

So my "red shutoff lever" is me taking off the lid of the air cleaner and pressing my palm over the intake.
 
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