I have been hunting down some vacuum problems with my '83 300SD and I think I've gotten as far as I can without a vacuum tester. My only remaining problem is slightly erratic shifting. The door locks work great, the car shuts off quickly, and the climate control is fully functional. I have been through all of the vacuum diagrams and everything is where it should be. I have replaced all hoses that seemed iffy. After reading through many threads here, I think I just need to spend a little time with a tester looking for small leaks and dialing things in. If anyone wants to help me with this I will gladly reciprocate with a beer or two. Thanks!

When you say erratic shifting exactly what do you mean. Is the trans flaring, not shifting at the right time or what. I'm to far away but I have an 83 SD also and may have had the same issues in the past.

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1983 300SD
200000miles

Similar to a set of metric tools, a Mityvac is standard issue for these vehicles. It's really impossible to maintain them without this tool. The cost is not excessive.

The shift points seem to move around depending on the engine temperature. I always warm up the engine before driving, but when I first take off the shift points seem pretty well spaced. Once I have driven for a while, power seems to drop off a bit, the shift points start to get very early, and it often seems to go straight from first to third. Third to fourth is almost always rough. Tromping on the pedal at any time does seem to bring back some of the correct spacing, and downshifting usually (but not always) seems to work as it should.

Have you actually counted the shifts to be sure it is using all 4 gears? There is a post about properly setting the transmission that really helps. I found that I had problems until I adjusted the shift controls on the trans and on the back of the IP. After that my trans was much more consistant.
I found the write up about adjusting the trans.
http://www.peachparts.com/shopforum/showthread.php?t=158216&highlight=adjusting+transmission

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1983 300SD
200000miles

I've seen that post but I don't recall reading anything specific about adjusting the modulator, which is what I believe you are referring to. I am getting all four gears except when it sometimes skips second. What's the IP btw...? Is it the injection pump?

This is a picture of the IP showing the vacuum modulating control valve, circled in red. I did a combination of adjusting this valve and the modulator on the side of the transmission to get mine where I want it. There is a small cone shapped cap on the side of the vacuum modulating control valve that you carefully remove and then you can adjust the screw you find under it. If you are going to try this you need to have a vac gauge in line that you can watch while you drive the car to test it. I teed into the live going to the trans and ran a long tube out from under the hood and in through the passenger window with a gauge on it when I did this.
I think I have some instructions from the shop manual that show how to do this and if I can find them I post them.

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1983 300SD
200000miles

Thanks Phil, I will see if I can't get my hands on a vac gauge. In the meantime the offer of beers still stands for anyone near S.D.

If you have a Harbor Freight near you you might see if they have a gauge. The gauge can measure pressure and vac. The gauge I used at first was off my mighty vac because it was there so I unscrewed it and put a fitting on the bottom. For this adjustment I found I didn't need a really good gauge because I was mostly looking for a general idea of what the system was trying to do but didn't need to know and exact vac number.

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1983 300SD
200000miles

I located a vacuum gauge and I started in on it this morning. After tidying up a few things I now have good vacuum going into the VCV on the injection pump, but none coming out. I have adjusted the linkage rod to give .5mm clearance at the stop at full throttle. What should I do next?

IF I remember correctly its more vac = softer shifts and less vac = harder, firmer shifts. This also means the harder you are accelerating the firmer the shifts and gentle acceleration get softer shifts.

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1983 300SD
200000miles

I took the VCV apart and the little plastic ball inside it was all gunked up. I cleaned everything as best I could and put it back together. Before when I would test it with my MityVac the needle would not even move when I pumped it up. Now the needle rises when I pump, but it falls back to zero just as quickly as it rose. I suppose it's time for a new VCV.

I'm in san diego and would be williing to "help", but I don't have much experience with vacuum, etc. It'd sorta be the blind leading the blind. I do know that sears carries a mityvac for less than $25.

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1982 240 D, 308,000 - 321,127 miles (sold)
1982 300 TD,166,500 - 226,000 miles
1998 E 320, 120,000 - 144,000 miles
2005 C 230 K, 26,000 - 77,000 miles (sold)

Hey, thanks for offering. I think (actually I hope) that at this point all I need to do is replace the VCV and do a little fine tuning. I also got access to a MityVac, but once again thanks for the offer.

So what can I expect to pay for a used VCV anyhow? Anyone know of any good used parts sources in the SD area? I know there is a place in OC (Hawaiian Gardens) that has a good selection of stuff.