Engine doesn't stop when you turn the ignition off - PeachParts Mercedes-Benz Forum

steverodie · #1 12-19-2002, 06:03 PM

Last night I turned the ignition off, but the engine kept running. I hit the emergency stop engine lever in the engine compartment to killt the engine. This problem happened once before on a routine oil change. The guy changing the oil dissconected a vac. line. Today I noticed it stopped the engine when I turn the ignition to the off postion, but it was kind of sluggish. I also noticed that the door locks were sluggish as well. Are these systems related? Where would I begin looking? Any suggestions woul help.

#2 12-19-2002, 07:08 PM

first off, do the brakes work well? if they dont you may have a different problem, however if the brakes still function normally then you have a problem with the vacuum shut off valve on the fuel pump. this is a simple repair...let me know about the brakes...

Scott L.

steverodie · #3 12-19-2002, 11:48 PM

The brakes work well. I seem to be only having a problem with the shuting off of the engine. I looked in a Hayne's manual and it also said that it could be a fault in the fuel shut off. Where is this located and what's the best way to fix this problem.

haasman · #4 12-20-2002, 02:20 AM

You've got a vacuum leak. Actually happens often when changing the oil on diesels (you do have a diesel?).

The lines get knocked. The fuel shut off is a diaphram that goes into the fuel injection pump. It sounds like you are loosing main vacuum.

Look in the area of your oil filter housing .... check each line very very carefully. Track the ones that go into the multi-group connectors. Push these connectors around at their junctions and see if there is a split.

Tells us your model and year.

Haasman

380SEGUY · #5 12-20-2002, 07:22 AM

I agree, sounds like the vacuum shut off diaphram has a leak.

If you have a vacuum pump, remove the hose that got knocked off the last time, hook up the pump and apply 20 inches of vacuum
it should hold for at least a minute.

If the vacuum doesn't hold you'll need to replace the shut off diaphram, It is an easy job but one that you can screw up if you are not careful.

I'm sure you can get the part at fast lane on this site. Then you remove the three screws that hold the diaphram in, being sure not to drop them. Then pull the diaphram very gently toward the fire wall while rotating the diapram toward the passenger side until it releases. Take the new diaphram and put it in with the vacuum connection facing uo and gently push it into the pump and rotate it toward the passenger side until it pops in, then rotate it back to it's normal orientation.

DO NOT push the diaphram into the pump and just install the screws.

This has the same effect as holding the accelerator to the floor and when you start it you will have a very bad day.

Good luck

Geoff Furr

ASE Master Tech

stevebfl · #6 12-20-2002, 08:43 AM

Since you are noticing a problem with the door locks that is most likely the problem. They are the most likely problem even if you are noticing a problem there.

The easiest way to test would be to by-pass the door locks. (I am presuming a 123 diesel here - 124 and 126 have separate door lock systems). To by-pass take a golf tee and place it in the rubber connection instead of the yellow vacuum line at the brake booster. Some models will have two yellow lines plug them both. The door locks will not work but they also can't leak in this condition so the car should then shut off.

If this locates the problem you will then need a vacuum gauge and some technique to solve the problem.

steverodie · #7 12-20-2002, 09:39 AM

My car is a 1985 300 TD. I'm going to check all the vav. lines near the oil filter to see if any are loose or cracked.

steverodie · #8 12-23-2002, 01:33 PM

I checked all the lines near the oil filter when I changes my oil the other day. None of them loose. I don't have a vac. gauge to determine if there is a leak or not. It sounds like it's the fuel shut off valve (after reading various threads) has gone bad. Is there any way to repair this valve? Or must you replace when it's about ready to give up. I saw that there was a "fuel shut off valve gasket". Are these parts related? Or do you need it when you install a new valve? Both of the parts are not too exspensive. The car still shuts down after several seconds of hesitation. Also the locks are very sluggish. The right rear lock has never functioned properly, but hopeully that's not related. The brakes still work like they should.