Hello, I (my wife) has a 85 300 Turbo Diesel that at times will run on and then will die (engine stops running) after @ 5 seconds of the ignition being turned off. At first I thought it was when it was cold outside but it is intermittent and I would like to fix the issue. It also seems like when it does this, the door locks don't always work so I assume it is vacuum related. Any tips, advice or suggestions are welcome.

I am more familiar working on Jeeps but not afraid to spin a wrench.

Buy a mity vac and pull the vacuum diagrams and start checking away.

W123 Vacuum InterLock Diagram

Dkr.

Here is a vacuum diagram that might be easier to use for the shut off specifically:
http://www.peachparts.com/shopforum/attachments/diesel-discussion/121864d1401410079-how-does-w123-shutoff-system-work-vacuum-diagram-engine-shutoff-plus-may-14.jpg

Your going to need a MightyVac. The first step would be connecting it directly to the shut off valve and pumping.

My intermittent problems went away just by replacing all of the small flex portions. It cost ~$10-15 and sure saved a lot of time. Look at any vacuum line near the oil filter, as they get disturbed more than others.

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )

As the others said. It is either a vacuum leak or the Vacuum Switch on the Sterring Colum Lock is not working right.

Go to Autozone and see if you can get the free rental fuelpump Gauge that is also a Vacuum Guage.

Disconnect the Vacuum Line at the Vacuum Shutoff on the Fuel Injection Pump. Start the Engine. Connect the Gauge to the Vacuum line you disconnected and should see no Vacuum on the gauge.

Leave it connected and turn the Key in the off position and then quickly look and see how much vacuum is on the Guage. Tell us what reading you get.

Also find some place to connect the gauge where you can read the vacuum from the main line. Becareful as the platic nipples on the main line break easily.

If you want to try with out the Gauge disconnect all of the vacuum lines that go through the Fire Wall and plug off the Vacuum side. Don't worry about the Black line as it is a vent line.
If it shuts off as it should like that you indeed have a leak somewhere inside of the Car.

__________________
84 300D, 82 Volvo 244Gl Diesel

Thank you for the responses and input and diagrams. Hopefully it will warm up a little this weekend for me to work outside on this.

Jonathan

One thing in general I would also recommend is replacing the vacuum elements pre-emptively when you can. You have one in each of the doors, two in the trunk (one for the fuel lid). These are usually the problem with vacuum leaks and I have found it is often easier to just replace them especially when you are doing jobs around them (i.e. pulling the doors apart) than to spend the time later trying to track down exactly where the leak is.

The vacuum lines themselves rarely have problems and if you have something leaking under the hood, it is a lot easier to find where it is.

Dkr.

Put a small transparent filter in the vacuum hose to the "shutdown valve" on the injection pump rear. When you see oil in the filter, you know that valve has a torn rubber diapragm. You don't want to wait until the oil gets sucked up to the ignition switch and drips on your foot and carpet.

But the OP's problem is more commonly from either a bad vacuum pump or vacuum leaks that overwhelm the pump. Need a vacuum gage to find it, as you block off various tee'ed hoses. Hoses are commonly knocked off when people are working under the hood, or they break off one of the 2 plastic nipples on the main vacuum tube.

__________________
1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans