Diesel Engine won't shut off

[callenderevent]

I have an 87 300TD diesel wagon that runs on after the ignition is shut off. I presume that this is a vacuum problem, but I don't know how to pinpoint the problem. By the way, the heat and air conditioning vents on the floor, either side of the console don't work. I don't think the two problems are related. When the climate control comes on, there is a series of clicks that sounds like they are coming from the glove compartment.These vents have not worked for several years. My first priority is the engine shut-off. Is it most likely a vacuum pump or a vacuum line or what. I would like to fix it myself economically, if possible. Thanks in advance for any help. John