This the second time that my 1986 300 DT started having trouble with shutting off. When I took it in before, the mechanic said it was a minor adjustment. This time a different mechanic says that when the car won't shut off when the key is turned its the fuel pump, which doesn't make sense to me. It seems to me it would be something associated with the ignition. I did have a rebuilt ignition switch installed in 2003. He wants to sell me a rebuilt fuel pump for a lot of money!!

 

I really dont know much about the diesels but I know there is a valve on the top left side of the engine that controls that. its near or beside the manual STOP lever. the lever might actually be part of the part im trying to describe.

there are some good guys on here that will probably be able to help you out with your problem

 

The diesel pump needs to shut off the fuel flow when it shuts down. There is not an engine ignition as it's diesel after all! The only ignition is the switch and that is for the starter and a solenoid in the pump to go into the shutdown. I'm still new to my car but I believe there should be a solenoid built into the pump to shut down the fuel flow. Perhaps someone a bit more experienced will chime in but I would look toward the rear of the pump as there appears to be a valve back there to assist in shutting it down. Do you have to manually push the lever on the pump to shutdown?

 

I believe my 300SD has the same shutoff system as your car, mine consists of a vaccum driven rod on the end of the injector pump that pulls on some linkage that in turn, shuts off the fuel going to the pump. If there is a leak in the system, the engine will attempt to shut off but never quite make it (as mine does). It could also mean a weak vaccum pump. Look on the end of the injector pump for a vaccum hose, that is probably the one you need. If the device is faulty a new one runs around 130ish. I would test it with a hand held pump before installing a new one. If it works then, its a matter of tracing vaccum lines up to the ignition key and searching for leaks...

Good luck!

 

I have a 240D and I think it is a vacuum line that runs to the brake booster or there abouts.

I had the same problem when I was doing some minor repair and knocked the vacuum line off. The car would not shut down or go into 2nd gear.

I am sure it has something to do with the vacuum. Do not let anyone sell you a new injection pump. Try this and let me know if I was correct.

Thanks and good luck.

Michael Bluestein
1983 240D
bluesteinm@gmail.com