1983 300SD - PeachParts Mercedes-Benz Forum

ralcala1967 · #1 03-10-2009, 12:29 AM

Hello All,

My 300sd shifts very roughly.
It is a variable thing, though is more rough shifting than not.

Also, I have noted my 300SD smokes a little more than other 300's even at idle, this is also intermitten. I know know they smoke they are diesels, but I seen other diesel and they really do not smoke at idle.

Central locking and climate control all work fine.

Any ideas? Is there anything that someone with limited mechanical skills and tools can trouble shoot?

Best regards,
Rafael

Diesel911 · #2 03-10-2009, 01:56 AM

Sounds like you may need to learn some more mechanical skills.
The milage of you car would be helpful.
Assuming your air filter is not restricted smoking is caused by things that keep the fuel from burnig well. Worn Injector Spray Nozzles not atomizing the fuel well, low compression, the valves being out of adjustment and the timing being off.
Of the bunch the Valve adjustment is the easiest to deal with.

Does the Idle smoke go away after the Engine is up to operating temp?
Does you car start easliy when it is cold?
When you have the idle smoke does it puff out or smoke continuously?

Diesel911 · #3 03-10-2009, 02:04 AM

The rough shifting could be due to too much vacuum getting to the Transmission Vacuum Modulator. There is a white plastic Valve on the back of the Fuel Injection Pump that controls this.
If the vacuum is OK your problem is most likely due to wear in the Transmission.
Here is some info that will explain things in detail:
http://www.continentalimports.com/ser_ic20242.html

I was having harsh shifting from 1-2nd. When I changed my Transmission Fluid I added some Lucas Transmission Sealer and that helped a lot. But the Vacuum issue needs to be checked first.
Do it yourself links:
http://www.peachparts.com/shopforum/diy-links-parts-category/

mrsaxman99 · #4 03-10-2009, 10:41 AM

This is why I wanted a manual so badly...I think my 300SD would be so much more fun with a 5-speed. And you can avoid all of this nonsense. Luckily, mine shifts fine...I hope it stays that way!

cmbdiesel · #5 03-10-2009, 10:56 AM

Try cleaning out all the tee's and orifices in your vacuum system.
Also, I would work on getting the vehicle to run as well as possible.
My experience (limited) with these vehicles is that as you get the car to run better and better, the shifting kinda comes along with it.
But, getting the vacuum to work properly is essential to good shifting,
there are numerous excellent threads about vacuum system.
Also, there is the Bowden cable that may or may not be an issue.
All things are interrelated on these cars, so don't take a huge swing at it right off, but work on getting as many neglected maintenance issues corrected first, and the smoke. Tried a compression test yet?

LUVMBDiesels · #6 03-10-2009, 12:08 PM

First off, get a MitiVac or similar vacuum pump gauge combination. Mine even can blow air out making it more versatile. Next hook the gauge into the vacuum line going to the transmission. Tee it into the line just past the white valve on the injection pump and see how the vacuum fluctuates during operation. You will need about six to ten feet of vacuum line to go from the place you tee'ed into through the window and into the cabin so you can look at the gauge while driving. Search the site for the proper vacuum levels.

If the vacuum is not right, replace the valve and all the hoses and fittings.

For the smoking issue take a look at the ALDA (square metal thing on top of the injection pump) if you can see a screw on top and not a black plastic cap it means that somebody has adjusted it already and probably made the fuel curve richer. You can try turning it 1/4 turn clockwise to see if this helps, but remember smoke is not a bad thing

I would get the valves adjusted regardles as they need to be done about every 15000 miles and I bet yours have not been done in a long time. When I bought my 300SD the valves had not been adjusted in years!

Do some more searches on this site for vacuum settings, ALDA, and valve adjustments. The information is out there, but you have to mine it.

Good Luck!

kerry · #7 03-10-2009, 12:19 PM

Quote:

Originally Posted by Diesel911

The rough shifting could be due to too much vacuum getting to the Transmission Vacuum Modulator. There is a white plastic Valve on the back of the Fuel Injection Pump that controls this.
If the vacuum is OK your problem is most likely due to wear in the Transmission.
Here is some info that will explain things in detail:
http://www.continentalimports.com/ser_ic20242.html

I was having harsh shifting from 1-2nd. When I changed my Transmission Fluid I added some Lucas Transmission Sealer and that helped a lot. But the Vacuum issue needs to be checked first.
Do it yourself links:
http://www.peachparts.com/shopforum/forumdisplay.php?f=82

Harshness or softness of shifts is controlled by vacuum. However, I'm virtually certain that too harsh a shift is not caused by too much vacuum but by too little vacuum. Hence, the odds are you have a leak in the vacuum system somewhere causing an overall reducation in vacuum and therefore harsh shifts. A simple test you can perform to see whether the vacuum leak is in the climate control system is to push the far right button, shutting off the climate control. If your shifts improve, particularly downshifts, then it shows you have a leak somewhere in the climate control system causing your harsh shifts.
Door lock vacuum on 126 SD's is created by an electric pump so that system is separate from the vacuum system associated with engine and transmission operation.

Diesel911 · #8 03-10-2009, 01:32 PM

Quote:

Originally Posted by LUVMBDiesels

First off, get a MitiVac or similar vacuum pump gauge combination. Mine even can blow air out making it more versatile. Next hook the gauge into the vacuum line going to the transmission. Tee it into the line just past the white valve on the injection pump and see how the vacuum fluctuates during operation. You will need about six to ten feet of vacuum line to go from the place you tee'ed into through the window and into the cabin so you can look at the gauge while driving. Search the site for the proper vacuum levels.

If the vacuum is not right, replace the valve and all the hoses and fittings.

For the smoking issue take a look at the ALDA (square metal thing on top of the injection pump) if you can see a screw on top and not a black plastic cap it means that somebody has adjusted it already and probably made the fuel curve richer. You can try turning it 1/4 turn clockwise to see if this helps, but remember smoke is not a bad thing

I would get the valves adjusted regardles as they need to be done about every 15000 miles and I bet yours have not been done in a long time. When I bought my 300SD the valves had not been adjusted in years!

Do some more searches on this site for vacuum settings, ALDA, and valve adjustments. The information is out there, but you have to mine it.

Good Luck!

Should he be adjusting the ALDA if his Injectors are shot, the compression is bad or there is another problem causing the Smoke?
While it may be that his ALDA needs adjusting the Smoke issue could be the Symptom of another problem.

vstech · #9 03-10-2009, 01:57 PM

Yeah, I really hope the OP gets needed maintenance done prior to digging into the vacuum, and alda adjustments!
get oil changed, get valve lash set, get timing checked and set chain stretch offset if needed, or replace chain and gears if needed real bad! THEN worry about injectors, and compression, and vacuum leaks and so on.
basics FIRST!