I have a 1982 mercedes 300d. Engine shuts off when door lock is activated.?

Question

Problem began with door locks not operating properly. Then car did not shut off properly. Car will shut off if driver's lock pin is depressed or if key is turned in lock from outside. Rear door locks still do not respond.

Answer 1

Your door locks, as well as the fuel shutoff valve, are vacuum controlled. In each case, there is a vacuum motor that operates the device. The weakness of this system is that a vacuum leak anywhere will cause the entire vacuum system to fail.

From your description, it sounds like the vacuum connection to the rear doors may be the failure point. This could be a bad vacuum line, or a failing vacuum motor. You would need to trace this out with a vacuum gauge. If you trace the vacuum system back from the vacuum pump (on the front of the motor), you may be able to isolate the door lock mechanism by plugging the vacuum connection. This would be a stop gap measure: your motor would keep running, but your central locking system would not work. .

Answer 2

Check your vacuum system. Your door locks operate using pneumatics (vacuum). The source is the engine itself. More likely than not, a hose is blocked as I was able to drive by '82 300CD for ~6 months before the leak was found. An excellent information source is the Discussion Forum at http://www.mercedesshop.com/

Answer 3

You have a vacuum leak somewhere. Have someone familiar with the vehicle's starting and central locking system troubleshoot to find the source of the leak.

Answer 4

I'm interested in buying a 80s model. I heard 1985 an on mercedes went to aluminum heads that crack,like Dodge Ram and Duramax.email me at [e-mail] want info to on how often to replace timing chain,and miles to rebuild transmission. Thanks.