ARG! Vacuum system, no shut off - PeachParts Mercedes-Benz Forum

NC Benz · #1 06-17-2007, 02:36 PM

I have looked at the vacuum diagrams, but my problem seems to be outside of the normal diagram.

I was cleaning the Benz so I could take my wife out for dinner last night. Before I went in to shower up, I took it for a quick run. All was fine.

We go out for dinner and park and it does not shut off. I tried a number of vacuum lines but all seemed OK, so we let it run while we had dinner.

Got home and the only way I could shut it off was dumping some Sea Foam in and covering up the air intake.... good night....

This morning I get up to look at things. I see a brown/black vacuum line not connected and I see no open connections. It goes back to the cabin. All of the diagrams show the engine compartment and not the cabin vacuum.

I have tried to plug just about every line I can think of.

How does vacuum stop the diesel? What the hell am I doing wrong????? The only way I can stop this thing is to Pull the fuel line.

toomany MBZ · #2 06-17-2007, 03:59 PM

Does your fuel shut off lever not work?. This is acuated by vac., usually, when you turn key. When you depress manually, you bypass the vac system. Check to make sure where your problem is. Where did you dump in Seafoam? The only way to shut off a diesel, is to starve fuel, or air. Plugging intake will work, as you have found out. The brown/black vac line on my '84 CD, goes from firewall to IP, just in front of oil filter housing and above RD bolt. Haven't a clue as to it's function. Odd this should happen as it did, yet sometimes you look at an old rubber connection funny, well...

kerry · #3 06-17-2007, 04:19 PM

You've got a manual shut off lever at the top of the linkage right near the valve cover. It should have a red label saying 'Shut OFF". There's a vacuum hose that goes to the shut off diaphram below that on the back of the IP. Trace it out. If it's disconnected, there's your problem. However, problems somewhere else in the vacuum system can also stop the shut off from working. To test the shut off itself, remove the original vacuum line, put a long piece of vacuum line in its place, start the engine and suck with your mouth on the vacuum line. A couple of good sucks should shut it down if your shut off diaphragm is good. If it shuts off ok that way, the vacuum problem is elsewhere.

NC Benz · #4 06-17-2007, 04:56 PM

Quote:

Originally Posted by toomany MBZ

Does your fuel shut off lever not work?. This is acuated by vac., usually, when you turn key. When you depress manually, you bypass the vac system. Check to make sure where your problem is. Where did you dump in Seafoam? The only way to shut off a diesel, is to starve fuel, or air. Plugging intake will work, as you have found out. The brown/black vac line on my '84 CD, goes from firewall to IP, just in front of oil filter housing and above RD bolt. Haven't a clue as to it's function. Odd this should happen as it did, yet sometimes you look at an old rubber connection funny, well...

AH HA! Thats where that bugger goes! I would have never have found that one! Thanks!

But alas.... it still does not shut off.

I have tried the STOP lever and it appears that a screw bolt is stopping me from pushing it far enough to turn it off. Hence I get to pull the fuel line every time.

I used to have one of he vacuum lines going back to the cabin.. a brown one that comes off of the tri-splitter thingy. If that line came off I could not stop. I am thinking it is related to a line running into the cabin. But there are no diagrams that show that vacuum run. at last I have not found them yet.

NC Benz · #5 06-17-2007, 05:00 PM

This picture helps me. Found out that some of my vacuum was not run proper. But still not shut off. Still think it is under the dash somewhere. I ntoice that I dont have any of the "limiting" orifices between the "Y" splitters. Is that a problem?

kerry · #6 06-17-2007, 05:11 PM

Try the suck on a hose test I described before going further. It will rule out a damaged shut off diaphragm.

NC Benz · #7 06-17-2007, 05:19 PM

Is that the diaphragm BELOW the check valve by the ADLA? In other words where the brown vacuum line goes?

Also, the black vacuum line that goes back to the cabin is not connected to anything and really not sure where that little thing goes.

Quote:

Originally Posted by kerry edwards

Try the suck on a hose test I described before going further. It will rule out a damaged shut off diaphragm.

NC Benz · #8 06-17-2007, 05:22 PM

I set up the vacuum line and sucked on it. I could hear the diaphragm click back and forth.

Biodiesel300TD · #9 06-17-2007, 05:28 PM

The black line that goes into the cabin is a vent. It's not supposed to be connected to anything in the cabin. There should be two brown vac lines in the engine bay. One solid brown one, which is the vac supply to the ignition. The other is brown with a blue line, which comes from the ignition and goes to the shut-off valve. You can see this line in the photo it goes in between the oil filter housing and in IP. Make sure that line is connected to the shut off valve on the IP and to the ignition.

To test the shut-off valve itself you can remove the brown line comming out of it and plug in a mity vac. Start the car and then give the mity vac a couple of pumps. It should shut the car of quickly and still hold vac. If it does then it's working properly, if not then the shut-off valve is bad.

toomany MBZ · #10 06-17-2007, 05:35 PM

May need to adjust "screw bolt" for lack of a better term. The straight threaded rods that have a ball and socket affair. Possible a PO tried to adjust idle via these things. {not in pic} The STOP lever eventually goes to IP near the B/B line that disappears under white thing on IP in pic. There is a black line that is a vent, somewhere, goes to nothing. Can send pic of my set up, I'm too low tech for here, PM me. Unsure of "limiting orifices".

kerry · #11 06-17-2007, 06:06 PM

Quote:

Originally Posted by NC Benz

I set up the vacuum line and sucked on it. I could hear the diaphragm click back and forth.

Will the engine shut off by sucking on it? If so, the shut off valve itself is working.
If that is ok, I would disconnect and plug the lines going to the doors and the HVAC leaving only the ignition and brakes hooked up. See if it works when isolated like that. If it does, the vacuum leak is in the doors or HVAC. If it doesn't, the problem is in the ignition vacuum circuit. (all this presumes you dont have a MityVac handy to test those circuits). Golf tees work well to plug the lines.

NC Benz · #12 06-17-2007, 08:24 PM

Quote:

Originally Posted by kerry edwards

Will the engine shut off by sucking on it? If so, the shut off valve itself is working.
If that is ok, I would disconnect and plug the lines going to the doors and the HVAC leaving only the ignition and brakes hooked up. See if it works when isolated like that. If it does, the vacuum leak is in the doors or HVAC. If it doesn't, the problem is in the ignition vacuum circuit. (all this presumes you dont have a MityVac handy to test those circuits). Golf tees work well to plug the lines.

You guys are AWESOME!!!

I ran vacuum direct to the diaphragm and the car shut down... WHEW! we are getting someplace....

I did ANOTHER go through of the whole vacuum system and found a very small crack in the 1 to 3 rubber splitter. I trimmed out the crack and VOILA! It was the kind of crack that left in a normal position you would not see and bent slightly would leak.

Thank you ALL! I did not realize that the black line was just a vent. Looks like I need to adjust that "screw Bolt" (hope I am not getting too technical on you here

) so that I can shut down the engine if this happens again. I bet my idle is too high as well. That bolt needs a very deep socket to loosen up the nut holding it.

Now I need to figure out why all of a sudden I dont have any turbo and why I cannot kick down to first gear... all of these items happened at the same time.... UGH

Biodiesel300TD · #13 06-17-2007, 08:31 PM

Clean the banjo bolts, they are probably clogged which causes no boost or low boost. There is on on the ALDA on the IP and one passenger side close to the firewall.

NC Benz · #14 06-17-2007, 08:38 PM

Quote:

Originally Posted by Biodiesel300TD

Clean the banjo bolts, they are probably clogged which causes no boost or low boost. There is on on the ALDA on the IP and one passenger side close to the firewall.

I did that already. Next idea?

Biodiesel300TD · #15 06-17-2007, 08:51 PM

Did you try changing the fuel filters?