Start to trace vacuum leak
 

Greetings,

Off & on for the last few weeks I have been trying to nail down why my car keeps running after I turn her off. I have a 1984 190d - excellent condition. All research points toward a vacuum leak. I have examined all connections under the hood and everything looks good. I thought I would turn her off, and then try the power door locks while she was still running. To my surprise the locks do not work. Just a few weeks ago they did. Also after she shut down I heard a little electric motor that kept running- even after I took the key out. I traced the sound to just about where you put in diesel. The motor stopped after a few seconds. I tried the door locks again and the little motor started again, ran for a few moments, and then stopped.
What in the world could this little motor be for? Thanks for your time.

Hugh Sr.

Your car has a separate electric pump for the door locks. IIRC that pump is under the rear seat. The pump sends vacuum to lock the doors and pressure to unlock.

Engine shut-off relies on the engine vacuum pump. There is a vacuum actuated shut-off device atop the injection pump. With the engine running, disconnect the brown plastic line leading to the shut-off actuator. Apply vacuum directly to the actuator. If the engine doesn't shut off or it takes more than 15 inHg to choke the engine, the shut-off actuator is bad. Now check for 15 inHg of vacuum from the brown plastic line. If you don't see that, there is a problem upstream. The system consists of a fitting along the vacuum line to the brake booster, a brown plastic line into the cabin to the key switch, a mechanical vacuum swtich attached to the key switch, and a brown plastic line to the shut-off actuator on the injection pump. Diagnose away.

Sixto
87 300D