Engine won't stop even with STOP lever - PeachParts Mercedes-Benz Forum

WD8CDH · #1 10-18-2006, 10:02 AM

Hi,

Yesterday after a 500+ mile trip when I got home the engine (85 300D) wouldn't stop when I removed the key. On the last stop in the driveway (and in the rain of course) removing the kay didn't even change the idle at all. Pushing the stop lever only slightly slowed the idle. Pushing a rag in the air cleaner intake slowed the engine slightly more but still no stop. I guess there are too many air leaks in the intake system.

The only way I could get the engine to stop was to stuff a rag in the intake while the STOP lever was pushed, the tranny was in drive and I loosened the idle stop by several turns. It still was relunctant to stop. By the way, the "oil cap test" was normal so not a catastrophic ring failure.

Does anybody have any ideas what I should look into next?

Previous stops had been uneventfull. About 4 seconds of unchanged idle and then 4 more seconds as the engine slowed to a stop on each previous stop. I know I must have a leak somewhere but the power locks have been disconnected and blocked off. The EGR and air bypass valve vacuum lines have also been plugged.

Thanks

Stevo · #2 10-18-2006, 10:42 AM

There is a brown vacuum line going to the stop switch on the aft end of your injection pump. Apply vacuum to it (suck on it or use a mity vac) and if the engine does NOT stop, you found the problem, bad vacuum switch. If it does stop report back for further help, you have a vacuum leak some place else

rudolfgreen · #3 10-18-2006, 11:00 AM

had the same problem and it turned out to be a bad vacuum pump.
rare and less likely, but possible. be sure to check your lines first.

WD8CDH · #4 10-18-2006, 12:34 PM

If it is just a vacuum problem, why would it not stop with the manual STOP lever?

Jadavis · #5 10-18-2006, 01:19 PM

Quote:

Originally Posted by Stevo

There is a brown vacuum line going to the stop switch on the aft end of your injection pump. Apply vacuum to it (suck on it or use a mity vac) and if the engine does NOT stop, you found the problem, bad vacuum switch. If it does stop report back for further help, you have a vacuum leak some place else

It's not going to be that simple. The vacuum switch just does the same thing the OFF lever does. His OFF lever did not work...

FWTW, when I turn my key off the engine shuts off immediately. It does not 'run as normal for 4 seconds and then slow down to a stop in another 4 seconds'. Uneventful, but not right.

-Jim

Jadavis · #6 10-18-2006, 01:21 PM

A temporary fix would be to put a valve in the fuel line before the IP. This may not be good for the IP. It would prevent the IP from delivering fuel to the injectors...

-Jim

BenzDiesel · #7 10-18-2006, 01:33 PM

Quote:

Originally Posted by WD8CDH

If it is just a vacuum problem, why would it not stop with the manual STOP lever?

Sometimes when the linkage is not properly adjusted, the stop lever does not have enough play or backward extension when it is pressed to completely shut off the fuel. When pressed, the stop lever linkage should continue to go backwards toward the valve cover and way past the position that it sits in at idle and if you would notice, you would see how it is functioning, which is: when pressed in a backward motion, the fuel is shut off. If one or more of the linkages are too short to allow for the sufficient backwards movement to fully cut off the fuel, then the car will not shut off, as you have stated. Anyway, the stop lever should shut off the fuel, regardless of what the vacuum is doing or not doing. Also, I'm really glad that it is a "shut off" problem and not a RUN AWAY problem, which are two very different things.

BenzDiesel

pawoSD · #8 10-18-2006, 01:42 PM

You do have to admit, with these cars the problem more often than not seems to be getting them to turn off, rather than having them not want to turn on.

They just love to be running.

How many other people can claim that about their cars?

WD8CDH · #9 10-18-2006, 03:36 PM

Before I disconnected and plugged the power door lock lines, I used the STOP lever many times and it always shut off the engine in 2 to 4 seconds.

iNeon · #10 10-18-2006, 03:43 PM

Quote:

Originally Posted by WD8CDH

Before I disconnected and plugged the power door lock lines, I used the STOP lever many times and it always **** off the engine in 2 to 4 seconds.

I bring nothing new to the table beyond pointing out to you that your typo and the subsequent filtering of it made me giggle.

Carry on.

Stevo · #11 10-18-2006, 04:51 PM

Quote:

Originally Posted by WD8CDH

Before I disconnected and plugged the power door lock lines, I used the STOP lever many times and it always shut off the engine in 2 to 4 seconds.

You should look after your vacuum problem because if the diaphragm is split in your shut off valve, then lub oil will be sucked into your vacuum lines and that leads to all kinds of places you don't want to go. The ignition switch is not a good place for oil

TWeatherford · #12 10-18-2006, 06:54 PM

Quote:

Originally Posted by pawoSD

You do have to admit, with these cars the problem more often than not seems to be getting them to turn off, rather than having them not want to turn on.

They just love to be running.

How many other people can claim that about their cars?

nice point. for future reference, wouldn't it be a bit simpler to turn off a very reluctant car to turn off, by just loosening the ip banjo bolt? this would result in a massive air leak and a dead engine. in an emergency, just cut a line somewhere close to the ip.

a2t · #13 10-18-2006, 08:15 PM

I love these old benzs. Unlike my fleet of VW's, you cant make these things stop!

Carson357 · #14 10-18-2006, 08:21 PM

likely the linkage is not properly adjusted for the manual shutoff to work properly, easy way to shut it off is to pop the linkage at the pump loose and pull up on it to shut it off, for it not to shut off with the key, try locking the doors and see if it shuts off, if not try pinching off the vacuum lines by the oil filter one by one and see if that helps, i have also seen the fitting on the booster line become clogged and not allow enough vacuum into the system, cleaning with a small drill bit usually works

Mustang_man298 · #15 10-18-2006, 11:44 PM

You know, this reminds me, when I did the diesel purge last week & finished, I went to shut it off via the lever to avoid sucking air, it didnt die off, got very near and chuggled on shuddering in sheel will to live, almost forgot I need to go back and tend to that before I have a real reason to...at least the underdash lines are fresh, had t ofix before I got it on the road, I think there was more oil down the carpet than was in the old engine...