I have a 2003 mb140 diesel van i cannot switch the engine off it continues to run even when the ignition key is removed

Check the vacuum hoses. on the fuel injector pump side of the engine you will see some 6mm hoses. the initial feed will come off the brake vacuum line toward the front to the engine in front of the injector pump. if you follow this line back you will get to a Y junction. from here the system splits to do 2 things. One line will run to the cylinder head to a thermovalve and from there to the back of the injector pump. I think this adjusts the timing of the injectors when the engine gets warm. The second line goes into the steering column to the ignition switch and then back to a shut off valve on the top of the injector pump. This is the line that turns the engine off and is probably the culprit. Check that the hoses are connected and that there aren't any obvious leaks. There is a third line (white) which also goes into the passenger compartment but it doesn't go anywhere else... it will have a filterchoke at the start of it so I think it is only to allow air to be sucked in if the vacuum gets too high

Check for s faulty shut of relay or failed solenoid for the stop on the pump