1987 300D Tach it out in 4th? - PeachParts Mercedes-Benz Forum

#1 04-29-2002, 07:48 PM

Hi,
I'm new to the diesel world but here to stay. I've put a little over 1000 miles on my recent purchase this week and it continues to improve in the power dept. I have an '87 300D-T with 220,000 miles.

The car is pretty quick off the line and accelerates well to about 80 mph. After 80, it shifts to 4th gear and will gain speed and rpm slowly to about 88 mph at ~3500 RPM. This is all I can get in Tennessee terrain. Is this as it should be?

The car cruises well between 80 and 85, which is all I need but if there is suppose to be more, I wanna go find it :p

BR,

Steve (8C>

#2 04-29-2002, 08:59 PM

If it's any help, my mom's 190D 2.5 (non-turbo) will exceed 100 MPH if given enough time, though I doubt it could make it to 110 (it would get darn close though). I suspect your 3.0 liter turbodiesel should, at the very least, be capable of the same.

-Joe

#3 04-30-2002, 03:34 AM

My 300SDL will accelerate well from 0 to about 100, then it hits a brick wall and takes quite a while to get to 115, it's max speed.

I made a movie if you want to compare:

http://www.zemkowski.com/movies/81-97.avi (3MB)

jcyuhn · #4 04-30-2002, 09:09 AM

The rated top speed of a 1987 300D turbo is 127MPH, so you've got a significant problem. First thing to check is whether the boost sense line to the aneroid is plugged. You can use the search function of this site to find past discussions on this topic; no need to explain it here yet again.

gsxr · #5 04-30-2002, 11:32 AM

Something is not right. I could cruise efforlessly at 100mph in Montana in my 1987 300D (and got 30mpg too!). Try clocking the car 0-60 with a stopwatch. Factory spec is 10.9 seconds (at sea level), but anything faster than 13-14 seconds is reasonably decent. Any slower and it just confirms your problem.

Jcyuhn is right, the first thing I would do is check the plastic tube from the intake manifold to the switchover valve, the valve itself (should be able to blow through it), and then the line out to the ALDA (square thing on top of the injection pump). After you check that (and do a 0-60 time), let us know the results...

Regards,

#6 05-01-2002, 07:09 PM

Hi and thanks to all who replied. Sorry for the delay, I've been out of town. I got back and stopped and got 3 feet of 5/32 vacuum hose on the way home.

I checked my 0-60 time before doing anything. About 25-30 seconds.

As I took the vacuum line running from the manifold to the overboost protection switch, it broke. It was completely clogged with nasty, coal black crud. I didn't buy any hard line so I just replaced the whole line with the rubber hose (for now).

I went down the road to the flat place and checked the 0-60 time. I had to get out of the car, go to the back and make sure that I had not accidently road tested my E420 by mistake :p . 11-12 seconds, WOW!

I know it sounds crazy, but I was happy with the car before. Now I am thrilled! As a bonus, it seems to have fixed some really hard shift problems as well. Does this sound right?

Thanks again for your help. I love this forum and my new car that I just got for $1.46.

Best REgards,

Steve Schwegler

gsxr · #7 05-01-2002, 08:16 PM

Yep, it's amazing what the difference is with the fuel enrichment circuit working, eh? If the line snapped easily, the rest of them are probably brittle too. You might want to replace the rest of the Tecalan (plastic) tubing, there's a good article with part numbers here:

http://www.mbz.org/info/articles/engine/vacuum/

Best regards,

jcyuhn · #8 05-01-2002, 09:56 PM

The hard shift problem was just because you had to put your foot so far into the throttle to get the car going without the fuel enrichment. If the engine is behaving like it should, a firmer shift when accelerating harder feels just right. If the engine is not making enough power, it feels all wrong. The reason it's shifting smoother now is because you don't have the pedal as far down to get the same acceleration.

I bet that's the easiet 50 horsepower you ever got!

190D22 · #9 05-02-2002, 04:35 PM

Hey turbodiesel, what was the orange light on the right side of the indicator light cluster? I noticed it was illuminated and my 190D doesn't have that light there.

#10 05-02-2002, 07:02 PM

Hi turbodiesel,

I noticed something else from your movie. My tach is at 3000 to 3100 rpm at 80 mph, while yours is at 3500 rpm. The PO put 205/65-15 tires on my car. Is the 1/2" making the difference in RPM/Speedo or is the SDL lower geared than the E Class?

BR,

Steve (8C>

gsxr · #11 05-02-2002, 07:34 PM

The 300SDL (W126) has different gearing than the 300D (W124). Both of my 300D/W124 run about 1000rpm per 25mph, or ~3000rpm at ~75mph (give or take a few percent). The 1/2-inch tire difference will only make a few percent difference on the speedo, maybe 2-3mph at that speed, or ~100rpm.

be459 · #12 05-02-2002, 11:53 PM

Check the following two things first:

(1) If you still have the Trap, get it replaced at the dealer for free.

(2) Check/Replace the fuel filters and air filter.

Good luck.

David