hey guys i have a 1983 mercedes 300 sd with 215,000KM on it. it has a shake at idle (when warm), and a stalling problem trying to stat when cold (if i hold the gas very lightly for about 20 seconds it will stay running).

i did a little research on here and starting messing around with the rack demper pin. i noticed small differences like now it is a little better at starting when cold, but shakes alot more. i want to buy the aftermarket one i see for sale here but am a little curious about a few things.

is there a certain way to take the original rack damper pin completely out? is there alot of small pieces that come out without it?

i read that there is a spring that gets ruined, but on the aftermarket one i do not see a spring at all (in the picture), or is it in the front where that little silver nose is?

do i have to use the original tightening nut in the front? because i dont see one with the aftermarket on in the picture.

thanks for all the help, george

Adjust your valves and clean your injectors before you mess with the rack damper. Feel free to send me half of the money that I just saved for you.

i have already adjusted the valves, and replaced the injectors that were nailing. i replaced both fuel filters, and when i put in the screw-on diesel filter i filled about 1/4 of it with trans. fluid to lube the system. still getting the same shake, and stall in the morning.

now you give me your money!!!!
just kidding thanks for the advice though!

thanks, george

You first loosen the locknut. Then the pin unthreads from the back of the pump. It's one piece. The locknut remains on the pin assembly.

The spring on the original pin is a bit softer than the new one. It's inside the unit and it acts on the "pin" at the very forward end of the assembly.

Yes, you use the existing locknut on the new pin assembly.

When you install it, you have to be a bit patient. You tighten it down until it contacts the rack and go about 1/2 turn more. Then try it for a day or so. See if the idle improves and the stalling is eliminated. If not, then go in about another 1/2 turn or so. You are looking for the point where it runs smooth but the start is not affected. In your current situation, it appears that the PO screwed the pin too far in an attempt to smooth the idle.

Remember, the pin is not a panacea. It won't cure an injector or a prechamber or a compression problem. It's just a small bandaid for stabilizing the rack.

Does it smoke at startup? Does your glow plug light come on? If answers are yes and no, then you might not be heating all your cylinders before you start, and that can cause rough starts at least.

Or, it could be, like Brian said, "an injector or a prechamber or a compression problem."

If the rack damper pin is not damping the rack, it will be seriously rocking and rolling hot or cold. You get more than just a rough or irregular idle.

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1982 300CD Petrol/Black Leather

A classic sign of a bad/maladjusted pin is when the car gets 'the shakes' after a highway drive.

I'm a big proponent of adjusting the pin, as it's easy to do and has made a very big difference on my car, but I would guess you have some other issues even if the pin isn't quite right. From what I've read I don't think it's normally associated with stalling.

__________________
Ralph

1985 300D Turbo, CA model
248,650 miles and counting...

Do the old style pins loose spring tension when warmed up?

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1982 300CD Petrol/Black Leather

when worn out. Just before I replaced mine, I held the old and new nose to nose and slowly pressed together. The new one compressed less than a 1/16" (1.5mm) to FULLY BOTTOM the old one. The spring rate was quite different.

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

You may have replaced the inectors that were nailing, but what you are describing is classic dirty injector. Just ask for a show of hands on how many insectors picked up crap after a very short time on the road.
A session of Diesel Purge will very likely get you some excellent results.

Thanks for al lthe replies!
I believe it starts shaking more when it is warm because it is not running as fast. When the car is warm and i just barely touch the gas pedal, the shaking goes away. The car smokes very little at start-up, but if i "floor it" while cold it smokes alot. The car has alot of power and alot of pick-up (I couldnt believe it, it must be more than my old 93 golf diesel). So i can't see it being compression.

I guess I will look around this site for how to do a diesel purge also since so far I found everything a needed. Thanks to the person/people putting this site together and its community!

Brian Carlton, thanks for that detailed reply on how the rack damper pin is removed/ installed.

George

He was kidding about the diesel purge, see the smiley face? Search for a thread by Beagle about injection if you doubt this.