I recently purchased a 300SD. The PO apparently had problems with the ignition switch and had separated the key cylinder and the electrical portion of the switch. The electrical portion was hanging out of the dashboard and he showed me how to turn the key and then use a screwdriver to turn the electrical switch to start and stop the motor.

I bought a used switch assembly from the junkyard and replaced the ignition switch. Initially, the car wouldn't start, until I removed one of the 2 vacuum lines that is attached to the ignition switch. With one or the other of these lines disconnected, the motor starts right up and runs great. However, it won't shut off without going under the hood to use the manual shut off. Later, I found that, with the motor running, I could connect the vacuum lines to the ignition switch, and it would kill the engine (without turning the key off).

I had disassembled both the original and the junkyard ignition switch to make one good switch. The original problem was that the ears were broken off the opposite end of the lock cylinder and so wouldn't engage the electrical portion of the switch.

Is it possible to assemble the electrical portion and the key cylinder portion out of sync with each other? I can't see anything inside the cylinder mechanism that would interrupt the vacuum from the lines feeding into the switch, and i have tried reversing where the 2 lines are connected.

I apologize if this issue has been posted before, but I did search a lot of posts with no success.

Rick