If that line is not disconnected, pull it loose and have a friend shut the car off while you check to see if it gets a vacuum. If not, start tracing that line through the firewall to the back of the key switch. If you don't find any loose fittings or disconnects, then check the second hose going to the key switch is hooked to it. If it is, remove it and see if it has a vacuum while the engine is running. If not, reconnect and start tracing it back through the firewall to it's supply. However, if it does have a vacuum, there's a chance the shutoff switch could have went bad.

Here is a diagram of the shutoff system.


And this posts conatins the rest of the vacuum diagrams.