Ignition switch problem? -- car won't turn off

87 300D 2.5T Yesterday I turned off the car and it would not shut off. So I put my foot on the brake and shifted it into Drive to kill the engine quickly.
It seems like this would be something in the ignition switch, but I'm not always certain. What else should a person check?
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If this is a 300D, there is no ignition, but you probably talks about where you put the key and turn it anti-clockwise . If the car went black, electrically, I would suspect some relay who missed turning off the diesel supply to the engine.

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A relay? I'll first check the fuses, then the relays. Thanks.
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A relay? I'll first check the fuses, then the relays. Thanks.
You are welcome.
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Cheesehead wrote:

Diesel engine shuts off via vacuum driven "relay". Normal and recommended procedure is simple; 1) open hood, 2) locate large red STOP sign on lever by injection pump (on driver's side of engine), 3) push it to stop engine.
The "ignition switch" has a vacuum switch that activates an engine shutdown vacuum actuator in/on the pump. It performs exactly the same action as a person pushing the STOP lever. Three failures can occur; 1) vacuum switch on "ignition switch" is failing, 2) vacuum actuator on pump is failing, 3) nylon vacuum line(s) have leaks.
To remedy, borrow/buy a decent vacuum gauge, check vacuum at idle. Should be about 22" to 21" at first distribution tee in vacuum pump line. Get vacuum system diagram, and start measuring vacuum where you can reach. Test injection pump vacuum actuator by supplying vacuum, then atmospheric pressure. If engine stops, then switch by steering column is bad, and needs replacing, or vacuum line from switch to injection pump is leaking.
/ JCH
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After further investigation ...
There is a little right-angle vacuum connection at the back of the injector pump mechanism. It's split. All the way up the side. Wide open. That's probably the problem. Now to find the part number ... Then tomorrow a.m. I will call the dealer to get one ...
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Cheesehead wrote:

Good show! A bit of carefully wrapped duct tape will do the trick temporarily until you get the new rubber tee. Incidentally, i run an old 1981 300SD (W126), while my wife drives a 1985 300D Turbo (W123). The 5 cylinder engines in both cars are essentially the same, but have small differences in the wiring, and the vacuum system lines. I keep an eye on that stuff. Do you need maintenance manuals (on CD)?
/ JCH
--
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I've found the spot right where the vacuum lines pass through the firewall to be another point of frequent failure. Had that with both the engine shutoff and the door lock feed on my 80 300SD.
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On older classic cars... I think 1993 and older... it is vacuum controlled and whenever there is a good vacuum leak, the diesel engine would have hard time shutting off.
On my 1995 E300D, they used electronic selenoid to shut the injector pump off... so newer diesels uses electronics to turn it off.
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