240D Won't Shut Off?? - PeachParts Mercedes-Benz Forum

dejan007 · #1 07-13-2006, 05:04 PM

I have a 82 merc 240d that after turning the ignition off and removing the key, the motor continues to run.
I am new to diesels and am not sure why this happens.
I can only shut the car off if I hit the lever under the hood.
Can anyone of you professionals help me out with this?
Thanks a million.

bgkast · #2 07-13-2006, 05:14 PM

Sounds like a vacuum problem. To shut off these cars the fuel flow must be stopped. First check the vacuum line connections on the ignition switch by removing the cover under the dash on the drivers side. Also check the vacuum line connections on the Injection pump. There are lost of good threads on this board about this problem. Good luck.

kip Foss · #3 07-13-2006, 05:42 PM

You have a vacuum problem. Either you are not getting vacuum from your pump or you are not getting it to your ignition switch.

Raise your hood. Find the fuel injection pump, which is on the driver's side of the engine next to the fender well. Find the small rubber/plastic hose that comes from the back of this pump up into the engine comlpartment. It ought to connect to other similar hoses around the brake booster on the fire wall. Disconnect this hose at the first connector near the booster and with the car running suck on the end of the small hose. You should be able to suck hard enough to stop the engine. If you can do this then your injection pump vacuum shut off mechanism is working.

With the car running put your finger on the place where you removed the small hose to the injection pump (ip). If you feel a noticeable vacuum then your vacuum pump is good.

This leaves your ignition switch as the culprit. This switch has one vacuum hose that goes in to it and one that comes out. The easiest way to access the switch is to take out your instrument panel. The easiest way to get the panel out is to remove your steering wheel. It is not absolutely necessart but just easier.

When you remove the instrument panel you will need a 10 mm wrench to disconnect the oil pressure line. IMPORTANT NOTE: After you have removed the panel DO NOT, repeat DO NOT start the engine. You will end up with a floor board and worse yet a crotch full of very black oil. Find an old oil MB guage and connect it to the oil line. I am speaking from experience.

Reconnect you vacuum hoses under the hood. Start the car. Remove the hoses at the ignition switch and see if you have vacuum. If you have strong vacuum then the problem is probably the ignition switch. As memory serves me I think you can remove the vacuum part of this switch with out removing the entire switch.

If you don't feel vacuum at the switch then you either have a bad vacuum pump or a plugged line. The switch vacuum line comes indirectly from the main vacuum line at the brake servo through the vacuum reservoir behind the driver's side front wheel well. If you don't care about having vacuum door locks or anything else vacuum then you can junp the reservoir and take a line directly from the brake servo area to the ignition hose. This will keep the car operable and give you time to chase down the leak.

bgkast · #4 07-13-2006, 05:50 PM

No need to pull the whole interior apart. I just replaced the whole assembly in my car from below.

kip Foss · #5 07-13-2006, 06:06 PM

It is not a question of 'pulling the whole interior apart' it is a question of removing two nuts and being able to work sitting on the seat rather than on your back on the floor with 30 years of crap fallinng into your face. Work smarter not harder.

carusle · #6 07-16-2006, 08:40 AM

Look at the vacuum connections just above your oil filter, is one not connected, that is the problem.

82cedes240D · #7 08-23-2012, 07:09 PM

Ok so I have a very similar problem to an 82 mercedes 240d not shuting off, but the wierd thing is when I turn the ignition off the car idles down the goes back up then idles down more then the first time then goes back up then shuts off I have checked all my vacuum connections and they all seem fine also I have checked the amount of vacuum and all checks out any ideas guys? Thanks in advance.

charmalu · #8 08-24-2012, 02:50 AM

You have a vacuun leak some where in the system, could be the vacuum shut off valve on the rear of the injection pump. the diaphram could have a small hole and not being able to pull the lever to shut off the fuel.

Here is a thread that has a diagram of the system and a good explanation of the system.
http://www.peachparts.com/shopforum/diesel-discussion/160169-w123-vacuum-interlock-diagram.html

Off your main black line from the Vac Pump to the Brake Booster you will see a line going to a yellow check valve next to the firewall. that Goes to your doors, fuel door and trunk actuators. and there is a yellow/grey stripe to supply the Vac in the trunk.

The brown line goes to your ignition switch, then back through the firewall to the Vac fuel shut off valve on the rear of the IP.

The green line is for the climate control pods under the dash.

You can isolate each system by plugging a golf "T" into the rubber connections to see what part has the leak.

Do you have a Mity-Vac? these are useful to narow down the leak.

Disconnect the line going to the fuel shutoff valve, and connect your mity-vac. start the engine and then see how much vac it takes to shut off the car, andor see if it will hold vac with the engine off.

You could also have a rubber connector that has dried out and cracked also.
Charlie

whunter · #9 08-24-2012, 04:00 AM

http://www.peachparts.com/shopforum/general-information/259240-hens-tooth-1985-300d-vacuum-filter-dark-black.html

http://www.peachparts.com/shopforum/diesel-discussion/105201-1982-240d-vacuum-system.html

http://www.peachparts.com/shopforum/diesel-discussion/229331-vacuum-pump-rebuild-thread.html#post1927867

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rs899 · #10 08-24-2012, 07:02 AM

Take a look at the check valve on the thick vacuum line from the pump to the booster. Mine has become porous and I can hear air going in there.