Of course, credit is due where credit is due: this awesome, sometimes too political forum! Ok, just a warning: this is a long read and some of you will find it "old news". But for others who are new, this might help you understand the things I've done that resulted in the greatest improvements.

Over the past year now, I've acquired what I thought was the perfect 87 300DT that I'd thought would be the perfect commuter vehicle. However, I made the mistake of buying Ebay sight unseen, but in the end, I did get back a big chunk of change and was forced to learn alot of body and welding work

Over the past 2-3 months, I've had time to focus on what I really wanted to do last year: making sure the engine runs close to factory specs. I'm a helluva lot closer, but I still have some questions and work to do. However, I am happy beyond belief as I've gotten my previously high mid-30s 0 - 60 times down to a best 12 seconds. A brief chronology of what I've done:

Phase 1
- I replaced all the fuel lines with the exception of the Tecalan ones coming off the fuel filter assembly. I changed out all the fuel filters including the screen off the tank.

- I messed around with the control shift cable (aka bowden cable, trans shift cable, etc) to adjust the previously very high shift points. they were shifting hard over 4k rpm. I generously compensated for that and brought them down 800 rpm to 3200 rpm. I alos adjusted the accelerator pedal nut to fine tune the pedal position. I also adjusted the trans modulator to soften up the shifts. I know I shouldve tested the vacuum issues in the engine bay, but I wanted to soften the shifts for every day driving and had a lot to read before testing the engine bay vac components.

- I replaced all the vacuum lines and the vast majority of the rubber fittings to eliminate those as possible sources for leaks. I highly recommend it. It was actually fun and gave me a sense of accomplishment to replace them all

The result of all this was a little frustrating because there was little change in the 0 - 60 times---still around the mid 30s. However, the shifting was better as i softened out the shifts as well as the shift point. However, i knew it was less than perfect.

Phase 2
About this time, the delivery valves started to leak. What luck actually. So I changed them all out and now I was pretty convinced I had a dry IP. I may pull it and change the other seals as Sixto suggested, but for now, I consider it dry and running well.

One night, my tranny decided to puke out all the trans fluid right in a restaurant parking lot. So I had to work on it anyways and given I still had crappy shifts, I decided to install a K1 kit from Mercedes. It had two effects: It softened out the 2-3, but also, the 1 to 2. I also changed the trans fluid with Valvoline high mileage tranny fluid as well as renewing the trans filter. I started to fine tune the bowden cable nut to kill some of the flare in 2-3 and 3-4, but I broke the nut off. Ironically, if it weren't for that, I would still have crappy shifting.

The 0-60 times went down from the 35s to I'd say the high 20s. I believe the fuel leakage as many of you had advised, was the key issue.

Phase 3
Because I broke the shift cable nut, I had to replace it. So I figured I'd do some more homework and read about a little spring kit from Superior. Kit # for my 87 300DT is K722A-D. I installed all the springs in the right combinations to address my shifting points. I also installed a new shift cable. After bolting everything back on and refilling with new tranny fluid, my shifting is near perfect. I can't tell you how much of a difference this car feels as compared to the day I bought it. Its literally night and day.

So last night I decided to tackle the engine bay vac components. I still have questions below, but one of the things I decided to do was to buy a turbo boost gauge because I was not convinced that it was working. I also ordered a turbocity.com turbo rebuild kit, which hopefully will arrive before the T-day holiday. So I hooked up the boost gauge between the intake manifold and the Y30 switchover valve (aka overboost solenoid) and then drove around. I could see that the turbo gauge was NOT working. Hmmm....not good, but VERY good in a way because now I knew that I have NOT been getting any turbo boost. So after reading for an hour or so through various print outs, one piece of advice changed my 0 - 60 times miraculously. I overrode the Y30 overboost protection valve by connecting the vac line from the intake manifold and into the rubber Y-connector off the ALDA (whose line normally feeds the top line of the Y30). I took a drive and I the first words out of my mouth were "HOLY S###" I took it for a few 0 - 60 runs while nervously watching the boost gauge in my hand and my times were in the 13s. I pushed it a little further and my times were in the low 12s!

The boost never got past 10 psi, so I know I could adjust it upwards. I also think I can enrich the fuel system by tweaking the ALDA a little. I think it could be faster off the line.

I plan to remove the intake manifold and do some cleaning, as I've found all the plugs were clogged with carbon deposits.

One of the side effects of all of this was that I had to adjust the bowden cable nut lower. Not sure why, but my shift points were again past 3000 rpm. They are now around 2400 - 2600 rpm at mild throttle.

Ok, that said, I still have some troubleshooting vac questions:

Switchover Valve (aka Overboost Solenoid - Y30)
I am pretty confident that my overboost solenoid is shot. Here's how I tested it. I unplugged it and then I ran an alligator clipped line from my battery's positive terminal to one of the leads on the bottom of the OS. No audible click was heard. I touched the other lead. No click either. Am I doing something wrong? Or is it truly shot? Also, I used a vac pressure tester and pumped in 10 Hg. The vac went right through. I tried 15 Hg and the same results. IIRC, it should only pass vac pressure when it hits 14.5. Am I doing something wrong here?

I'll want to test the other switchover valve as well as the vac amplifier (Blue UFO). Is the testing procedure for the other switchover valve the same?

1 Pin Pressure Switch (S66)
Sorry folks, but I'm a total newb to using a multimeter. The manual states to test this, you need to use an ohmmeter. I did so, but not sure if I am testing it correctly and interpreting the reading correctly. So I pulled the electrical connector off the 1-pin. I put one end of the probe on the pin and then the other probe on the inside portion of the connector. The reading said "1". The manual states that the "pressure swithc (S66) is open in the off state. I believe "1" equates to "open". So am I testing this correctly? And is my result showing that S66 is operating correctly?

Plumbing the Boost Gauge
There appears to be a test fitting just to the left of the intake manifold fitting. Can I plumb that for my boost gauge?

Edit: pics totally out of order

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On your multi-meter, 1 is not an open circuit, 999 is.

The overboost solenoid: Shoot some WD-40 through it. It should be a straight-through with no power to it, common to plug with soot.

The Tee / pressure gauge hookup is fine.

__________________

Gone to the dark side

- Jeff

Jeff,

Thanks for the response and thanks for clearing up what 1 vs 0 is. That said, am I performing the test correctly (where I am putting the probes)? If yes, then this device is not working.

I just ran some WD40 through the solenoid and at first, nothing came out. But then I shot it again and a bunch of black soot came out as you wrote. Wow, you're not kidding. I sprayed a few more times until it was clear. I'm going to allow it to dry up before hooking it back up.

I'm looking at my previous post, and fully awake now.

On an ohm-meter / DMM, you will read zero with a direct short = zero resistance.

An open circuit can read many different things depending on the meter, auto-ranging meters will often find some connection, and give numbers other than 9999 or infinity, but the open circuit is infinity or OC (for open circuit), or 999 or anything large.

__________________

Gone to the dark side

- Jeff

I'm not sure I read your expectations of the overboost VSV correctly but it should be open to pressure (or vacuum) normally. When you apply power to the pins, it should close. It gets +12V when the key is in run position. The pressure switch on the manifold provides ground when there is 1.0-1.1 bar in the manifold.

I'm from the camp of tapping a boost gauge line between the VSV and the ALDA for a sense of what the ALDA sees. That way you know when to clean the manifold port and VSV

12 seconds at 10 psi is great for a car this age. Do you really need a new cartridge or are you addressing oil leaks?

FWIW, mine gets closer to 12 psi by 2500 rpm but overall it doesn't feel like it's getting to 60 mph in 12 seconds :/

Sixto
87 300D

Have you done your valve clearance and timing yet? That will make a nice difference too.

__________________
My Primary Driver - '85 300CD - 4-speed conversion, 2.47 rear, lowered, euro headlights, rebuilding (not restoring so much)

Wife's - '08 Saab Sportcombi Aero

Riding a '03 Yamaha Warrior

Six,

Billyboborama sent me a great synopsis of the relationships between the ALDA, turbo, VCVs, etc. and in it, he provided me instructions on how to test the overboost solenoid (VCV). Apparently (ahem...embarassed clearing of the throat), I did not put ground to one of the pins. So I tested, it it clicked when presented with 12 volts.

Billybob suggested the same too re: tapping the line thats between the ALDA and the VSV. I'll wire that up tomorrow night. Not sure where I'm going to mount the gauge. I'm not going to put it on the ashtray. Too low.

I also neglected, but i also just cleaned the S66 connection too. So I still have not figured out how to test the S66 pin. Do I need to supply power to it from the ignition? Or can I test it cold? If so, where should the probes touch?

also, I have not done any valve clearance or timing chain work. i'll do some homework on it. thanks for the suggestion, lowrider

if it's a an 87 300 turbodiesel then I guess it has an om603 engine. No need to adjust the valves as they're automatically adjusted.

Your 0-60 mph times should be about 11 sec.

__________________
1992 Mercedes 190D 2.5 turbo 5sp manual. EGT+boost gauges. Boost controller set to ~14.5 psi. 1 1/4 turns on full load adjustment. LPG injection. Next in the list is water injection.

8.7seconds 0-55mph, and it should do it if you have no trap-ox anymore.

__________________

Gone to the dark side

- Jeff

Thats only 55mph, the standard measurement is 60mph (sometimes 62 when comparing foreign cars.) That last 5mph can make a significant difference in time.

I know, just posting the original time from the '80s.

__________________

Gone to the dark side

- Jeff

Deni and Jeff,

Yes, its a OM603. Thanks for the info re no valve adjustment needed. Man, I'm getting spent working on this!

Jeff, thanks for the stats. I know I'm close to factory specs, so I feel better now