Hi,
Reading some posts on the subject , the problem appears to be the fact of the vacumn shutoff controlled by the ignition key. Although I don't have one installed yet in my 83 TD, I did put a mercedes diesel engine/tranny in my 1973 International Travelall(Suburban) and this is how I controlled engine shutoff.
On many older American 80's cars on the firewall, you will see a small barrell shaped solenoid with 2 vacumn lines going to it and a 12v plug attached. Thats a 12v. vacumn solenoid. Many chryslers used this with the torqueflight trannys and emission controls and to delay when vacumn advance would kick in.
On the solenoid you will see 3 ports. 1 is uually plugged. You can make it normally open or closed. How mine is wired is that When no electric is supplied the valve is open so vacumn pulls through it. So, this is what happens. when I turn on the ignition key, the valve is energized and closes, NO vacumn can pass thru it so rack gets no vacumn, car runs. When I shut off the key, The solenoid is deenergized and the vacumn passes thru it and pulls the rack down, Engine shuts off. I notice a 1 second delay from when I shut off key to when engine stops.
TO install on a benz, find the 2 vacumn lines going to key switch, the supply , and the line back to the rack and, hook them to your solenoid. Now when the remote starter signals the ignition with the proper delay relay for the glow plug cycle, the solenoid engages, closes off vacumn and car starts. The opposite will happen when you signal to shut off the car.
If your looking for solenoids in a yard, look at old Dodge Darts, Lebarrons etc. The more emission controlled crap on the car, the better the chance of seeing 1 or 2 solenoids. Also if the solenoid ever fails while driving and the car shuts off, all youhave to do is disconnect the vacumn supply line and plug it. The car will start right back up and You can use the engine shutoff on valve cover to kill engine until you replace it. AS far as new solenoids, STANDARD ignition might carry it. Hope this helps, MIke Moran