I have a 82 300d turbo. The car will not shut off. It started off that when you turned the key off it would shut off by hitting the stop lever under the hood. Now though that doesn't even cut it off. Last time I had it on I had to disconnect a fuel line to get it to shut off. Does this sound like I just need the stop solenoid or might something else be wrong?

 

If the stop lever won't shut it off there's one problem to start with. fix that to see if you have any other problems

 

I have heard that a vacuum leak can be the cause for it not to shut off.

 

lwbrewer is right. The Engine should stop when you use the Stop Lever.
Make sure none of the Injector Fuel Return Hoses is running under the Stop Lever and preventing it from being pushed down all the way. Also you need to hold the Stop Lever Down until the Engine stops.
It could be that the Stop Lever Linkage is out of adjustment.

The Vacuum Shutoff (solenoid) on the Fuel Injection Pump can be tested by disconnecting the Vacuum Line going into it and connecting a separate piece of Vacuum Hose to it and using a hand pumped Vacuum Tester (like a Mighty Vac) or you can simply suck on the end of the Vacuum Hose to Creat Vacuum.
If the Engine shuts off normally when you do that the Vacuum Shutoff is OK.
(If when you disconnect the Vaccum Hose from the Vacuum Shutoff some Engine Oil comes out if it; that is an indicationg there there is a leak in the Vacuum Shutoff and it is pulling some Oil from inside the Fuel Injection pump.)

Check your Vacuum Lines to be sure they are all connected and there is not cracks or holes in them.

There is also a Vacuum Shutoff Valve that is attached to the Steering Wheel Lock. This is what you actuate when you Turn the Key in the off position. The Vacuum Hoses in that area could be leaking or the Shutoff Valve itself could be no good.

Are you having any other Vacuum related problems like Door Locks that are solw or not working or Power Brake issues?

 

There does not appear to be any other vacuum related issues