I have a 1980 240d that always shuts off when the ignition is turned off but sometimes the shut off is immediate and sometimes it will run 8 to 15 seconds after the ignition is turned off. The engine seems to gradually lose RPMs until it quits. I have been unable to find a vacuum leak under the hood. The door locks also work slowly. I read in another forum about a vacuum leak around a door lock causeing a similar problem. However my 1984 300SD has a different vacuum pump for the doors. does anyone know whether the 240D door locks works off the same vacuum pump as the fuel shut off valve. Any other ideas?