82 240d engine won't shut off - PeachParts Mercedes-Benz Forum

Missouri240D · #1 08-21-2008, 03:33 PM

i've read some of the posts concerning this problem; sucking on hoses and getting oil in your mouth, but can't i just run a kill switch off of the battery somehow?

yellowbenz · #2 08-21-2008, 03:46 PM

No, the only way to shut it down is to shut off the fuel supply (or block the air intake but that's not practical). There is a vacuum line that goes to a shutoff valve on the Injection pump. Get a mighty vac and start the troubleshooting process. Did you change the oil recently? Maybe you knocked the vac line off the shutoff on the back of the IP. It's a brown line I think? The shutoff valve may have failed and the might vac will help determine if that is the case. The other place to check is the ignition switch.

Stevo · #3 08-21-2008, 04:05 PM

If you get oil in your mouth from sucking on the brown vacuum line that would tell you the shut off switch is bad . If you do find oil in the line its a good idea to fix the problem because when that oil works its way up to your ignition it will cost more $ .

kerry · #4 08-21-2008, 04:46 PM

Sucking on the shut off valve is the solution for those without a mity vac. What you have to understand is that unlike a gas engine where the engine is stopped by cutting out the spark, diesels have to be stopped by cutting off the fuel or air since there is no spark. The ignition switch is not electrical when it comes to shutting off. It simply allows vacuum to travel from one line to another, sucking on the fuel shut off valve.
To put it another way, your car does not suck at the moment. You need to figure out why not. There are two main possibilities: either the vacuum diaphragm in the shut off valve has failed, or more likely, there's a problem elsewhere in the system (ie a vacuum leak) reducing the vacuum to a level that cannot actuate the shut off valve. Usually these leaks are in the door or climate control system. Since you probably have manual climate controls, you might have a leave in the door actuators.
You can exclude the doors by disconnecting the yellow vacuum line under the hood near the firewall and plugging the fitting where it was plugged in. If you do this and the engine shuts off, you have found your problem.
But in any case, a serious 123 owner should own a MityVac.

Missouri240D · #5 08-21-2008, 09:47 PM

thanks to all. this website really helps an ignorant benz owner. guess i'll start sucking.

JimmyL · #6 08-21-2008, 10:42 PM

You just need a Mityvac, then this is one of the easiest problems you will ever run across. {I don't know if that is good news or bad}
Forget "rig" jobs such as the kill switch off the battery. Specifically for this problem it doesn't shut down electrically, but in general most fixes are easy enough where a rig job just isn't necessary.
Go into an issue determined to "fix" the problem. Lots of folks here to help you do that......