Now it starts, but won't stop
 

Spent part of my Veteran's Day troubleshooting a cold-weather hard-start. Located two glow plugs that were bad, and subsequently replaced same (#'s 3 and 4).

This morning (temps in the low 40's) the '85 300TD started right up with barely a nudge from the starter. Problem surfaced when I reached my destination, key to "Off", and the motor continues to run.

Opened the hood, and used the manual stop lever to shut her down. Restarted the motor, engaged the door locks, and tried again; no luck as the motor continued to run.

I know I've got a vacuum problem somewhere, but what/where is the most likely culprit?

All door locks work fine, but the transmission now no longer shifts smoothly, especially 2-3 and 3-4.

Standing by with a Mighty-vac at the ready...

You pulled loose some vacuum lines or cracked the main vacuum line (to the brake booster) when you were doing the GP work. Recheck all your vacuum connections.

On my '87 300TD I accidently knocked off a hose leading down toward the IP. Engine would not turn off. Since I had been working in that area I found it quickly. Seems to me it also happened one other time toward the firewall on the left side.

If you start at the vacuum pump and work away from it you should find the problem w/o needing to apply the Miti . . .

There is a 4-way where one of the 'ways' goes to a yellow check valve at the firewall. I had same symptoms, installed small inline checkvalve for a temp fix. Fixed shifts, doorlocks, and shutoff. If you're like me you probably have a leak in the dash somewhere, i.e. vac element. I don't want to pull the dash just yet. Heater still works BTW.
I'll go out when I get home and post a pic. But in the meantime replace all the little crumbly vacuum connectors that you can.

OR- like the others said you knocked a vac conncector loose, or you nudged an old one and aggravated it to the point that it is now leaky. Some of these connectors will swell up making the seal a bit wonky.