Rough Idle on W116 300SD Turbo Diesel
 

Hello,

I need some help to get a fix on my rough jumpy idle on my 300SD Turbo Diesel. I have had the valve adjusted, new fuel filters, air filter, etc.

I still have a car that shakes at idle like a pro-street rod racer with a high lift cam.

What should I look at?

:book:

...More info:
 

Howdy,

What year is the car? The OM603 six-cylinder in the '86 and '87 have an idle speed control system and an "anti-jerk" solenoid that helps with idle smoothness.

The five-cylinder OM617 in the earlier cars will become rough and idle poorly due to injectors getting old or dirty (among other reasons).

Checking for air leaks in the fuel system and doing a compression test is a great place to start...;)

It's likely to be caused by bad motor mounts if the engine itself isn't misfiring. All of these diesels vibrate, but when the mounts go bad they transmit the vibration to the car so you notice it more. Have the mounts checked, and if they are collapsed, as I suspect they are, have them replaced. It is not a hard or expensive job and the results are dramatic.

rack damper bolt
 

Try adjusting the rack damper bolt

Having similar issues with my '83 SD. Being a 116, I think, chassis does it have a 617? RD bolt on mine not culprit. I've got a thread going on the subject.

I have an 84 300sd with a rough idle problem as well. I've done all the filters, valve adj., and now the injectors, but it idles rough as heck. What's next? IP timing?

Thanks.

...if you have one. My 80 W116 300 SD doesn't have one ( I wish it did:().

Rick

How do you go about adjusting the rack dampener bolt? Where is it located?

rack adjustment
 

its located on the rear of the injection pump, if I remember correctly it has a lock nut, size 14mm and the rack bolt is a 12mm, with engine running loosen the lock nut, adjust the rack bolt a bit at time watching for the engine to smooth out. That least thats how I did it on my 79.

Hmm... does anyone have a picture?

On mine it was a list of things each removing a little vibration.
Listed from the top down what had the most effect on reducing vibratin on mine.
Rebuilt injectors
Updated Rack Damper Screw
Fix an air leak by changing fue inlet hoses
Replaced motor and transmission mounts (none were broken but some were soft due to oil saturation).
Replaced one Engine Shock/Damper (I ruined one getting it off)
Readjusted Rack Pin Damper.

In fact no one has mentioned replacing the Engine shock or the Engine Shock mounts if these are not OK they will not help reduce vibration. Also a goodTransmission Mount will help decrease vibration.
Idle speed set too low.

The Rack Damper Screw can be see protruding from the middle rear of the IP in this diagram where the pump is shown completely assembled; and is item 259 is the O-ring and item 257 is the Rack Damper Screw in the Exploded View.
http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=123132&M=617%2E912&GA=722%2E118405&GM=716%2E005++++++++++++++717%2E400&CT=M&cat=1 43&SID=07&SGR=045&SGN=01