car keeps running... what if I let it? - PeachParts Mercedes-Benz Forum

JHZR2 · #1 11-27-2002, 03:53 PM

Hi everyone,

Once in a while my 300D keeps running. The times when it does this are really without rhyme or reason, sometimes I could have been using it, generating plenty of vacuum and it wont turn off, and sometimes I can have it sitting for a few days, run it for 5 minutes and it wont turn off... Kind of odd.

But anyway, my question is regarding shutoff. The other day it was raining, and the car wouldnt turn off. I tried all sorts of things, locking and unlocking doors, climate control on and off, etc., and couldnt get it to turn off. Eventually I got all wet (dressed up in suit too), opened the hood, killed it, etc.

So, my question is, what if I turn off the car, put the key in the off position and pull the key out, turn off everything, and lock the doors and leave it? It can either somehow generate vacuum in some amount of time and turn itself off, or keep running until I return to it an hour later. Is it OK to do this? The battery dummy light turns on, but since there isnt really any electircal load, I dont see why this owuld be a problem.

Any info would be appreciated, thanks

JMH

billrok · #2 11-27-2002, 07:21 PM

Well you certainly could let it idle. Diesels can idle for hours with no real problem but why would you want to. Just pop open the hood and press the manual shut off. When you get a chance, stop at Pep Boys and buy a Mity Vac and check your vacuum shut off switch. If it leaks, buy a new one. If it doesn't, look for the vacuum leak and repair or replace the bad vacuum line. It's not a difficult repair and a great DIY project.

Stevo · #3 11-27-2002, 08:01 PM

JHZR2

Letting a diesel idle for a long time is not a good idea

as carbon will build up. Suck on the vacuum line to the IP (shut down switch) and if that shuts it down replace the switch if not get that mity vac and find the leak but letting your engine idle is not a good thing. It seems to me the vacuum switch was only $+-30.00. That mity vac is a good thing to have around if your gona be into MBs ,you'l need it sooner or later

Good luck

leathermang · #4 11-27-2002, 10:47 PM

A diesel only uses about 1/80 th the fuel that a gas engine does to idle... Why Stevo thinks it would cause carbon to build up I don't have a clue...However, in many places it would be illegal to leave it running..... due to theft potential... like leaving the key in the ignition...
I suggest that you install a cable into the drivers compartment which would allow you to activate the manual shut down lever without opening the hood.... when your vacuum switch fails...

JohnM · #5 11-28-2002, 10:10 AM

When my wife was driving the car regularly, I came home to find the car idling in the driveway. I asked if she was going somewhere and she said, “no, it does that some times and it eventually shuts off”. I suspect that it was merely because the leak at that time was in the door lock actuators and they leak more while unlocked than locked if the boot has a hole in it. (or maybe it was the other way around? Whichever it was, she figured it out and didn’t tell me there was a problem.) I now drive the car and disconnected the doors from the vacuum system in the driver’s footwell (and plugged the source tubes) until I get a chance to do the repair.

In any event, it sounds like you have a small intermittent leak (the worst kind). That small leak will most likely get bigger and more regular until it won’t shut off at all, ever. It’s repair time or isolation time if you can live without the leaking device.

Gobble, Gobble!
Happy Thanksgiving

JohnM 1983 240D 160K 4 sp manual

can-do · #6 11-28-2002, 10:57 AM

Greetings JMH,

I would say the reason your diesel isn't shutting down is either the injection pump shut-off valve is leaking not pulling a vacuum or your vacuum shut-off switch at the ignition key switch is clogged up not holding that vacuum when you turn the key to the off position. Do a search on shut-off valves as well as shut-off switch as I have made several posts on both when this problem happened to me. In either case the engine won't eventually shut off without the presence of vacuum to pull the IP to the no fuel position. Both parts can be bought from Fastlane quite cheap so I'd fix the problem instead of letting it run.

Charles

240-diesel · #7 11-29-2002, 09:31 AM

JMH , I just had that problem , motor kept running on . Then got out vacum tester because my fuel door would not lock anymore and I took the unit out and found out it was bad , so I just bypassed it until I get a new one. But motor still ran on and had to shut it down manually a few times , I went around and around a few times and started looking under the hood and found that on the main vacum line cigar hose there is a two port check valve , one of the ports was not drawing in any vacum I tried to poke it clean but still no good . I plugged it off and put a tee branch off the one next to it and now the motor shuts right down every time. All vacum works but does not hold door locks all day, sometime I will check all of the other fittings and replace the cigar hose . Hans.