ENgine will not shut off on my 1984 Mercedes 300D turbo

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Terry - 13 Feb 2007 05:25 GMT

I turn off ignition switch everything shuts off except th engine. I
have to open the hood everytime I want to shut it off please help me.

Terry

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Richard Sexton - 13 Feb 2007 13:17 GMT

>I turn off ignition switch everything shuts off except th engine. I
>have to open the hood everytime I want to shut it off please help me.

http://articles.mbz.org/engine/diesel/nostop/

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Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
1970 280SE, 72 280SE | Home pages: http://rs79.vrx.net
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weelliott@gmail.com - 13 Feb 2007 17:27 GMT

In that article that Richard linked to it mentions sucking on that
line. If ti takes 15 to 20 pounds to get it to operate, I don't think
that you can do that with your lungs. but I might be wrong. Either
way, I'd suggest getting a short section of rubber hose and sliding
that over the end of the hard plastic line and sucking on that
instead. I use an old syringe like you get with epoxy to troubleshoot
vacuum systems. On my 300D the vacuum line was actually at fault. The
rubber connections will start to leak once they get old. Although that
might also be aggravated by exposure to various things. I just put new
rubber connections everywhere I could find and everythign started
working better. The vacuum system does everything in that car.

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Richard Sexton - 13 Feb 2007 19:21 GMT

Ectually I wrote the article. It'll actvate at about 7 pounds
and yeah you can easily so better than that with your lungs.

>In that article that Richard linked to it mentions sucking on that
>line. If ti takes 15 to 20 pounds to get it to operate, I don't think
[quoted text clipped - 7 lines]
>rubber connections everywhere I could find and everythign started
>working better. The vacuum system does everything in that car.

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Karl - 14 Feb 2007 16:41 GMT

Pounds of vacuum?!?

In the USA, vacuum is measured in inches of mercury.

If you can do 7 pounds with your lungs, then you can suck a golf ball thru a garden hose :)

> Ectually I wrote the article. It'll actvate at about 7 pounds
> and yeah you can easily so better than that with your lungs.
[quoted text clipped - 10 lines]
> >rubber connections everywhere I could find and everythign started
> >working better. The vacuum system does everything in that car.

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Richard Sexton - 14 Feb 2007 16:49 GMT

>Pounds of vacuum?!?
>
>In the USA, vacuum is measured in inches of mercury.
>
>If you can do 7 pounds with your lungs, then you can suck a golf ball thru a garden hose :)

I don't remember details, whether it was pounds of mm or Hg.

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Tom Plunket - 13 Feb 2007 23:22 GMT

> http://articles.mbz.org/engine/diesel/nostop/

I've been meaning to ask; if I hook a vacuum pump to the shutoff valve
and give it a squeeze, the car shuts right off. When connected
"normally", shutting off the key results in the car stopping after a
couple of seconds, so it seems the vacuum eventually gets there when
left to its own devices. What parts in the system might I start looking
at? Richard's article says that the vacuum hose goes to the ignition
switch, is that relatively easy to access if the kick panel has been
removed under the dash?

thanks,
-tom!

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Richard Sexton - 14 Feb 2007 16:44 GMT

>> http://articles.mbz.org/engine/diesel/nostop/
>
[quoted text clipped - 6 lines]
>switch, is that relatively easy to access if the kick panel has been
>removed under the dash?

This is really hard to do without a vacuum tester. You can get a
"Mighty Vac" (or some silly name like that) from any half-decent
car parts store. There's two versions, the plastic one and the
metal one. The plastic one is to be considered disposable; get the
metal one.

What you'd do it test the system bit by bit. There's not really a lot
to it and what you're most likely going to find is a black rubber connector
that has an almost imnpercevable crack and that's letting air in.

You CAN test this without a tester but it involves sticking tubing in
your mouth and sucking. Hope you like the taste of oil :-(

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Tom Plunket - 14 Feb 2007 18:48 GMT

> >I've been meaning to ask; if I hook a vacuum pump to the shutoff valve
> >and give it a squeeze, the car shuts right off.
>
> This is really hard to do without a vacuum tester. You can get a
> "Mighty Vac" (or some silly name like that) from any half-decent
> car parts store.

Yeah, that's what I meant when I said "vacuum pump" above. ;)

> What you'd do it test the system bit by bit. There's not really a lot
> to it and what you're most likely going to find is a black rubber connector
> that has an almost imnpercevable crack and that's letting air in.

Ok, I'll dig in. Ugh good times. My day under the passenger carpet was
not fun, but that was 'cause I didn't know what went where (and was
disappointed to find that the vacuum parts all worked, but there were
other things that have cause the automatic locks to not function). I
suppose it could be worth it just to get a bunch of those junctions and
go through and replace 'em all as I come across them, huh?

-tom!

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Richard Sexton - 14 Feb 2007 19:26 GMT

>> >I've been meaning to ask; if I hook a vacuum pump to the shutoff valve
>> >and give it a squeeze, the car shuts right off.
[quoted text clipped - 15 lines]
>suppose it could be worth it just to get a bunch of those junctions and
>go through and replace 'em all as I come across them, huh?

It probably is. Look around under the hood and pay special attention to
all the rubber connector. Take each one off, examine it throuroughly
and put it back on.

The cynical view has it that the mere act of taking them off and
putting them back on will cause them to fail. But the connectors
are cheap at the dealer. It really wouldn't hurt just to replace
them all.

Be aware you cannot get color coded vacuum lines any more, just
black. Also, the tubing sometimes fails at the juction of the
connector so sometimes you have to cut it back half an inch or so.

If your door locka aren't working anyway you probably ought to just
plug up that branch of the vacuum circuit with a screw (don't use
a golf tee, they fall out)

Dollars to donuts though it's under the hood and easily fixed.

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Tom Plunket - 16 Feb 2007 02:38 GMT

> >I suppose it could be worth it just to get a bunch of those junctions
> >and go through and replace 'em all as I come across them, huh?
>
> It probably is. Look around under the hood and pay special attention to
> all the rubber connector. Take each one off, examine it throuroughly
> and put it back on.

K, thanks.

> The cynical view has it that the mere act of taking them off and
> putting them back on will cause them to fail.

I'm of that mind also, especially considering they've been there for
almost 30 years.

> Be aware you cannot get color coded vacuum lines any more, just
> black.

Yeah, I've wondered about this; are there different diameters at play in
this car, or are they all the same size? Autohaus has different colors
available, it seems, but I haven't bothered measuring the ones on my car
to make sure they'll work. Certainly, if I can at least get almost the
right color, I'd prefer that to black.

> If your door locka aren't working anyway you probably ought to just
> plug up that branch of the vacuum circuit with a screw (don't use
> a golf tee, they fall out)

I intend to fabricate the springs. One of these days. ;)

> Dollars to donuts though it's under the hood and easily fixed.

Excellent, I'll take a peek. First stab will be to put the vacuum
tester on the vacuum hose and shut the car off. Somehow I didn't even
think of doing that when I was fiddling with it last time...

thanks for your insight,
-tom!

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