Sometimes car wont shut off even with the stop lever? (83 300SD) - PeachParts Mercedes-Benz Forum

Travis_k · #1 12-09-2011, 06:54 PM

Sometimes my car wont turn off when i turn the key to off, but so far its too intermittant to diagnose. I fully intent to find the problem and fix it, but with how often it happens now I dont think that would be possible. The thing that concerns me though is that most of the time when that happens the engine will just shut off with the stop lever right way, but other times the idle only slows a little bit no matter how long I hold the lever down, and returns to normal idle when i release it. Every time this has happened i just wait a minute and try again and the stop lever will shut it off. Does anyone know what might cause this? Linkage out of adjustment? Something in the injection pump failing? Im really not sure. I do carry a wrench with me to loosen the fuel lines if it ever completely fails to shut off, but I would rather fix it if I can.

Diesel911 · #2 12-09-2011, 08:54 PM

Remove the Brown Vacuum Line that goes into the Vacuum Shutoff on the Fuel Injection Pump and plug the Brown Line.
If there is Engine Oil in the line you have a leak in your Vacuum Shutoff Valve; oil is being pulled through some crack or leak in the diaphragm.

Attach a length of Vacuum Hose to the Vacuum shutoff and while the Engine is running suck on the Line. It should shut off like that. If it does you most likely have a Vacuum Leak somewhere else.
Look at your Vacuum Lines and see if anything is disconnected.

Built into your Idle Adjustment screw is a sopring loaded Rod. When you use the Manual Shutoff your throttle lever on the Fuel Injection pushes up on the Rod and moves the Throttle Lever into an area where it will shut off.

The Rod has been know to stick due to rust. And, as you said the Linkages could be the Issue.
I think I have also read that a miss adjusted Rack Damper Screw can do that also.

You might try pulling up on the Throttle lever in the idle direction and see if it will shutoff.

Also when I first got my Car I found that someone had routed one of the Fuel Injector Return Lines under the Manual Shutoff and it interfeered with using it.