engine won't shutoff

[why-is-my-username-taken]

I have a 83 240d that doesn't turn off when i switch the key to off and the emergency stop is really hard to depress and even then, it doesn't immediately shut off the engine. what are the causes and remedies to my problems. Thanks.

[tyl604]

If it is like my 300SD, then you may have a shutoff valve problem. A vac line goes from your ignition switch to the shutoff valve. When you turn the engine off a vacuum in this line pulls back a lever inside the shutoff valve and the engine dies. It could be that the plastic vac line is bad but my money is on the shutoff valve itself. Takes maybe an hour to replace it. Located in the back of the injection pump - also called a shutdown valve or actuator.

Of course it may be different for a 240.

See a pic in post #11 of 1981 300SD No shutoff - how do I find vac leak? However this is a 300SD.

[Sugar Bear]

Apply vacuum to the shutoff on the back of the injection pump. Vacuum applied should shut the engine down promptly, if it doesn't the shutoff valve is leaking internally and needs to be replaced. If it does shutoff promptly then the valve is good but it isn't receiving vacuum.

Check it and we'll go from there.

Good luck!!!

[tyl604]

SB is right. Just hook up a Mityvac to the nipple on the shutoff valve and pump it up. Should shut down the engine immediately. My first shutoff valve lasted from 1981 to 2015; the second one lasted six months. However no problem since then with the second replacement. Think I got it from Bill Grissom on the forum.

[BWhitmore]

Check the shutoff valve using a Mityvac hand operated vacuum pump. As stated before if the shutoff valve is good the engine should shut off immediately when vacuum is applied.

[Diesel911]

Well, it is a system.

Disconnect the vacuum line at the fuel injection pump shut off. If there is oil inside the tube the diaphragm is porous. However, like on mine it is porous but still works. You don't need a mighty vac to see if it will shut off. Connect a clean length of vacuum line and simply suck on it. It is supposed to shutoff as was said.

The mighty vac (handheld vacuum tester) is good to see if the pump shutoff will hold vacuum.

Next there is a vacuum shutoff switch on top of your steering Colum lock. That can leak or malfunction. Have not read of a way to test that.

Other vacuum leaks else wear can keep your engine from shutting off.

Concerning the manual shut off all of the linkages are supposed to have specific lengths.

If you have an MW Type fuel injection pump when you use the shutoff it pushes up against a spring-loaded rod. If the part of the rod that is inside of the tube is rusted the rod may not move as far as it is supposed to go to shut off quickly.

Obviously, it any of the tubing is cracked it can leak vacuum. Those 2 and 4 way rubber connectors tend to do that.

[vstech]

How many times can you press the brake pedal before it is difficult?