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  #1  
Old 07-19-2005, 09:51 PM
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Location: Boulder, CO
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No 3/2 valve on '82 300td

I know this topic has probably been beaten to death, but...

I recently bought an '82 300td and have hence inherited a few problems I am motivated to fix. The following are problems I am experiencing that I believe are all related to the vacuum system: very bad automatic shifting, key will not shut off engine, locks don't work, brake pedal needs lots of force to apply brakes. I took a look-see under the hood and noticed one black hose that is not connected to anything. From looking at my '84 300D, this cord should go somewhere behind the engine (transmission maybe?), I can't tell where it ends. More importantly, I don't have anything where the 3/2 valve should be on the IP. All that is there is what looks like 3 metal prongs. Is this why the shifting sucks and the car won't turn off with the key?? Thanks in advance...

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Old 07-19-2005, 10:38 PM
Craig
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Quote:
Originally Posted by fennybergs
I know this topic has probably been beaten to death, but...

I recently bought an '82 300td and have hence inherited a few problems I am motivated to fix. The following are problems I am experiencing that I believe are all related to the vacuum system: very bad automatic shifting, key will not shut off engine, locks don't work, brake pedal needs lots of force to apply brakes. I took a look-see under the hood and noticed one black hose that is not connected to anything. From looking at my '84 300D, this cord should go somewhere behind the engine (transmission maybe?), I can't tell where it ends. More importantly, I don't have anything where the 3/2 valve should be on the IP. All that is there is what looks like 3 metal prongs. Is this why the shifting sucks and the car won't turn off with the key?? Thanks in advance...
Yes, the vacuum leak will cause all these issues. Recommend that you take a look at these vacuum diagrams:

http://www.peachparts.com/shopforum/showthread.php?t=105297

Note that there is one black hose that is supposed to be vented. It should run through the firewall and vent under the dash. There is also one line that goes to the transmission. An open connection anyplace in the system will cause a loss of vacuum to all these components. Troubleshooting usually requires blocking off one branch connection at a time untill the symptoms go away, then chasing down the leak. Not difficult, but tedious.

Good luck.
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Old 07-19-2005, 10:46 PM
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Join Date: Jul 2005
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3/2 valve?

Thanks for the quick reply Craig. What about the lack of a 3/2 valve? Is this the source of the engine not shutting off? Is it essential to have vacuum going to this?
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Old 07-19-2005, 11:45 PM
Craig
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I don't have my 300d with me to look at so I'm not sure where the "3/2 valve" is in the system. Can you identify it from this diagram?

http://www.ultrahot.com/vacuum/engine.jpg

To try to answer your question, the entire vacuum system is interconnected so that an open line anyplace may cause a loss of vacuum to everything. From what you said about your brakes, I assume that you are not getting vacuum anyplace. If you look at the diagram, there is a large black vacuum line from the vacuum pump (Item 7 - located on the front of the engine) to the brake master cylinder. Smaller vacuum lines tee off to the door locks (several small lines that go through the firewall), as well as to the ignition switch and controls associated with the IP. The circuit that shuts off the engine is shown as the brown line from the tee through the firewall to the ignition switch (item 1), then the brown/blue line that goes to the fuel cutoff on the IP (item 3?).

If it was me, I would start by temporarily blocking (golf tees) all the smaller branch connections from the large line to the brake master cylinder just to make sure the vacuum pump is working and/or there is not a major leak in that part of the system. Once you verify that the power brakes are working, you should be able to work your way out to the line that feeds the ignition switch. I don't think the "3/2 valve" is directly in that circuit (I may be wrong), but if any of the components are missing it may result in a loss of vacuum that is disabling eveything.

If the missing component is the source of your leak, it should be fairly easy to replace the missing part and restore the system. Hopefully, your leak is under the hood where it's easy to get (not under the dash or in the doors).

Hopefully, this will give you a starting point. The last time mine had a leak it turned out to be the door lock for the fuel filler which took several hours to track down. I'm sure there are other folks here who are more familiar with the details of the system, and can give advice that will get you to a solution faster.
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  #5  
Old 07-20-2005, 12:16 AM
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Quote:
Originally Posted by fennybergs
Thanks for the quick reply Craig. What about the lack of a 3/2 valve? Is this the source of the engine not shutting off? Is it essential to have vacuum going to this?
On that model the 3/2 valves operate the EGR. If the supply line to the 3/2 valves is plugged, nothing else will be affected. If the line leaks, everything else that is vacuum operated will be affected.

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