Let me first describe the problem, from take off until 2000rpm the car's acceleration is ok, but from 2000-4500 it hits a wall. If anything it slows until it shifts and again builds momentum until the same RPM range where the car boggs down. Trying to accelerate onto a highway is flat out dangerous, especially on an uphill ramp. Obviously the problem is related to the turbo boost or lack of, but I am not sure it is even working. Below is a list of what I have tried but so far no luck.
[ul][*] 1. Replaced all filters
2. Cleaned manifold connector
3. Cleaned EGR and line, tested connected & bypassed, not it
4. Cleaned both lines from alda to swithover valve & hollow nut on manifold, & SOV, tested connected & bypassed, not it
5. Cleaned line into turbo
6. Looked over soot filter (603 142 02 94), normal carbon build up
7. Cleaned White/Blue line from turbo to VAC[*] [*]
[/ul]
I know the one thing left is the ALDA but I am no where close to normal performance so something else has to be wrong, Is there anyway to test the turbo or another area where I could look? There is also a large amount of black smoke when I reach 2000 & up. Thanks for your help ahead of time

Camper
96 E300 (108000)
87 300 SDL (181000)
82 300 D (103400)

 

You didn't mention the waste gate! It almost sounds like the waste gate opens after it begins to build rpm above 2000.

You should take a vac/pressure guage and tee it in between the switchover and intake. I route the vac/pressure gauge and hose up and under the wiper blade so I can see it driving, close the hood, but make sure you don't kink the guage hose closed, and go for an acceleration run. If you are not getting between 10 and 12 psi, you are not making boost!

Two reasons possibly why......#1. In order to develop boost, assuming the turbo is functioning, the ALDA must enrich the fuel. A. Check alda with a Mity-Vac. It should hold vacuum, if not, seals maybe worn, not uncommon. B. Alda is rusted seized (happened to me) remove alda and clean off rust and apply oil.

The second possibility may involve the waste gate. There is a single rubber hose, about a 1/2 inch in diameter, and about 6 inches long (the only one down there) under the forward section of the turbo, clamp this off and see if you can produce boost, if it does, don't go much above 12 psi.

You can also by-pass the switchover and go direct from the intake to the alda, if you think the switch is bad. Also, check that the vac hose barb/connector at the intake manifold isn't clogged up as they have a tendency to do such........Try that and let us know.........

 

Tested vacuum on the ALDA, and it did not hold. I tested another 87 300SDL and it did not hold either. Then I tested an 86 300SDL which runs good and it did not hold, the only car that held solid was my 83 300D, I also tested a 91 or 92 350SDL and it held at 6Hg. It seems unlikely but probable that three 86/87 SDL's aldas did not hold vacuum, and why would the 86 perform up to standards. If the ALDA is not holding a vacuum, is there any reason to check for boost. Is the ALDA repairable so it will hold a vacuum, because finding a good one might be difficult at this rate.

 

Ran the line btwn ALDA & SOV and tested with the vac/pressure, well as I suspected no boost, I didn't even get it up to 1 psi, tomorrow I will clamp the wastegate and test, then I will move on to the ALDA, but what can I do to the ALDA to improve the vacuum or make sure it is functioning properly, could the turbo be locked up, anything else I could check please let me know Thanks

Camper
83 300D
87 300SDL
96 E300

 

I have taken apart an ALDA and they are pretty simple. Inside there are two brass discs that are hollow. They appose each other. One has a rod on it that extends out of the alda body and connects the IP. That rod has seals around it and it is these seals that wear. Depending on how much wear in the seals around the rod will determine how much force the rod will have to push the part inside the ip that enrichens fuel. A leaky alda may still perform, but at some point it will fall short. Building boost also requires fuel to be enriched at the same time. Without alda enrichment, no boost!

Seals I have read are available, but I'm sorry I have no direct link. Try http://www.mercedesshop.com/shopforum/index.php3 and look in search under ALDA.