Vibration at Idle was Rack Damper Adjustment in 1982 300 TDT

Well, I installed the rebuilt injection pump from Pacific Injection Service. It helped, but the vibration was still bad enough to shake the screws out of the rear door. I contacted Mike at Metric Motors,
the place that remanufactured my engine, and asked his advice. He said to send him my injectors and that they would go over them, identify any problems they might have, correct those problems and then send them back to me.
Metric did find small leaks and evidence of contamination in two of the five injectors. They sent me replacements for those two injectors. Last evening I got the injectors back in with all new round seals in each prechamber.
The problem seems to have been related to the injector issues as it is much better now. I had changed the big fuel filter just before all this trouble started last fall. I think contamination must have gotten into the fuel system when I changed that filter and that that led to all the subsequent problems.
I still have to adjust the idle and perhaps mess with the rack damper bolt a little, but the car ran smoothly last night and I think I finally have what for a long time seemed an intractable problem solved.
Paul Fretheim
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I certainly do empathyze, as I have gone through this same problem. Mine was solved by a compbination of stopping one (1) injector leak, idle adjustment, and finally, the new engine hitting about 3,500 - 4,000 miles, whereupon it smoothed out and generally runs very sweet. I believe I still have a bit of a problem with my injection pump needing to be rebuilt, and I am going to do that; mine does not have the rack dampner bolt adjustment.
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Thanks for the update, Paul. Interesting. Mine vibration problem at idle in my 1982 300TDT went away with new fuel filters. It seems like the whole fuel system is in an oddly delicate balance that can be upset by any number of things. I apprecite you sharing this as it seems to be a common issue. Glad you got it fixed!

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There is still a funny thump or rumble or shake sometimes now that the idle is set back. I checked my motor mounts and it looks like at least the one on the left side has been torn apart by all the shaking. I have a pair of mounts on order and will try and get them installed without removing too much in the engine compartment.
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Just like I suspected... injectors... Way too long to diagnose the injectors.
Get that motor mounts replaced before you even adjust anything more.
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I am still not convinced it was the injectors. This was slow for a number of reasons including that I didn't have time to work on the car for months at a time.
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Well, those of you who advised that the problem sounded like a broken motor mount were correct. I now have the smoothest running 1982 300 TDT in the world!
After all the work on my injection system, including a newly rebuilt pump and carefully balanced injectors, I had the engine running so smoothly that it hardly rocked, even with a broken motor mount. Now that I have a new mount the car is running the best it ever has since I bought it in 1992. On the coldest mornings it starts instantly, like a gas car.
Smooth as silk, and powers over the massive mountain passes of Death Valley National Park on cruise control at 50 mph.
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What really bothered me is that you had your engine rebuilt and they didn't even change the motor mounts...
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That was my fault. I did the removal and replacement of the engine. How I overlooked replacing the motor mounts is a mystery to me, but I must have because the one I just replaced was too totally shot to have only 20,000 miles on it.
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When you refer to "Motor Mount" do you mean the entire forging of the mount pylon, or are was it the vibration dampener/absorber part of the mount?
I have exactly the same problem, and have yet to find the cause. My motor mounts were to have been replaced during my recent rebuild, but I am now suspicious...
Certainly happy to hear that you have your problem solved, as there is nothing nicer than a smooth-running Mercedes diesel.
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It is a simple rubber block mount. Look it up online and you can see a picture of it.
Autohausaz.com is a good source...
http://www.buymbparts.biz/ is also a great source... Rusty's. He used to have .com address and I think lots of his customers lost him.
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Congrats on finding the cause. A friend of mine has an '84 300SD that has started doing that bouncy thing at idle. I told her to have her mechanic consider the rack damper, remembering your earlier posts (she tried the fuel filters already which had worked on my 300TDT). Now I'll have to tell her to have them look at the mounts. Thanks for the update and glad to hear your car is back to top notch.They are such great cars!

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