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1983 300 CD
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22 Posts
Discussion Starter #1
This is my first Mercedes diesel and not sure if I have a problem or not. My car has 165,000 miles and has the original injectors in it. There is a slight shake in the engine while it idles and it does not smoke. Please listen to the exhaust in the video and tell me if that is a normal sounding 617 exhaust or if I have repairs to make.

Currently I have:
Checked timing chain stretch, 1 degree off.
Checked compression, 395-400 lbs. each cylinder.
Changed fuel filters.
Adjusted valves, twice.

I have many years experience with V8 gas engines and the exhaust noise in the video sounds like a miss-firing cylinder (to me anyway).

Thanks in advance and this is a great site!

1983 300CD

 

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1984 300D
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5,070 Posts
You did not say if the miss/saking changes after the Engine is up to operating temp?

Air leaks inthe Fuel Fupply system can cause a rough idle.

The stock Injector Nozzles have two small drilled passages in them (see attached pic) #14 and #15 that get plugged with Carbon.
The drilled holes #14 and #15 are mostly there for idle and low amounts of fuel so it has an effect on the idle.
Sometimes something called a Diesel Purge will clean the Injector Nozzles sometimes not. Do a search for Diesel Purge.

If your Fuel Injection pump a Rack Damper pin, the other pic of the Fuel Injection Pump the yellow arrow points to what I call the Rack Damper Pin. Loosen the lock nut and slowly rotate pin in or out until you find the spot that works. There should be more detailed instruction somewhere on this forum. Don't over do turning it in; you do not want to adjust your idle speed with it.

If you have a 5 cylinde Diesel it is not going to idle as well as a V8 gasser.

Also take a good look at the Motor and Transmission mounts as well as the Engine Shock absorbers (if it has them).
 

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1983 300 CD
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Discussion Starter #3
300Dman,

Thanks for the info. The rough idle is a little worst when the engine is hot.
I did the Diesel Purge (2 cans) yesterday and changed the filters, no noticeable changes.

Today I will try the Rack Damper pin adjustment. In reviewing other posts they indicate I should have a gold spring (updated spring) on the Damper pin. I will post the results later.

Also, I will go ahead and order new replacement injector nozzles (165,000 miles on originals).

Thanks again!
 

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1984 300D
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5,070 Posts
When I rebuilt my Injectors I replace the Spray Nozzles with Monark made in Germany Nozzles. Because the stock Bosch nozzles are made in India and do not have a good reputation and also because I did not like the little drilled holes feature that can fill with Carbon.
The Monarks do not have the drilled holes, cost less and are higher quality. Mercedessource is one of the Places that sells them.

Also I recommend against the Diesel Giant (has a web site) type Nozzle Swap.
When I rebuilt mine I did the complete job including lapping the flat surfaces and setting the Nozzle Opening/Pop Pressure whith a Nozzle Tester.
If you do not have the equipment find a local shop that will do the rebuild with the nozzles you supply.

I do not agree completely with the way he lapped his parts but this is a better description rebuilding Injectors than most.
vincewaldon.com - HOW-TO: Rebuild Diesel IDI Injectors

Another source of information
Repair Links
DIY Links by Parts Category - PeachParts Mercedes ShopForum

PeachPartsWiki: Do It Yourself Articles - Mercedes Vehicles

While the pic below is of a Bosch Nozzle for the newer Mercedes this is the same feature that the Monark Nozzles have that replaced the drilled holes in the Spray Nozzles.
 

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1982 300D Turbodiesel 212K or so, it doesn't work anymore :-)
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216 Posts
doesn't sound like its skipping...sounds like its a diesel...
 

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1980 300TD
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162 Posts
Changing nozzles and balancing the injectors isn't a bad thing at all. But I'm kind of with neosama on this one. It sounds a little bit loud maybe but not arrythmic or "off."

In other words: lower your expectations and everything will be wonderful. :D
 

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1983 300 CD
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Discussion Starter #7
Adjusted the Rack Damper pin today and that made a huge difference! The motor now idles with hardly any movement at operating temperature. Highly recommend this adjustment.

Monark spray nozzles on order and I'll post the outcome.

Thanks for the reassurance on the diesel's exhaust. Still getting use to that skipping sound.

Thanks again guys!
 

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1984 300D
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5,070 Posts
Adjusted the Rack Damper pin today and that made a huge difference! The motor now idles with hardly any movement at operating temperature. Highly recommend this adjustment.

Monark spray nozzles on order and I'll post the outcome.

Thanks for the reassurance on the diesel's exhaust. Still getting use to that skipping sound.

Thanks again guys!
I am happy something worked.

In the past I bought a brand new Gold Rack Damper Screw only to find it did not help much.
Rebuilding the Injectors took away most of the shake and next was adjusting the Valve.
After that it was replacing the 3 mounts.
After that the Rack Damper Screw adjustment was able to work on what was left of the shaking.
 

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1977 300D, 1980 450SL, Genuine Buddy 125cc Scooter
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252 Posts
sounds like mine, i think.. My tailpipe is smooth and solid without that patterned bump bump bump bump bump that yours has.

Under the hood sounded fine tho. maybe you have loose hanger(s)..I dunno Im new to diesels too.
 

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1983 300 CD
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Discussion Starter #10
I rebuilt my injectors this weekend. Pop tested the original injectors as soon as I removed them. They were well balanced but, two of them were squirting a stream, not spraying a mist.

Replaced the Spray Nozzles with Monarks and balanced them with the Pop tester. The miss/bump sound is gone and the exhaust is now smooooooth sounding!


1983 CD
 

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´85 300D Estate, Unimog 411
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115 Posts
I rebuilt my injectors this weekend. Pop tested the original injectors as soon as I removed them. They were well balanced but, two of them were squirting a stream, not spraying a mist.

Replaced the Spray Nozzles with Monarks and balanced them with the Pop tester. The miss/bump sound is gone and the exhaust is now smooooooth sounding!


1983 CD
the first video sound good to me, PLEASE send a new video for comparison
 

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1983 300 CD
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Discussion Starter #12
I sure will. As soon as I get it off the jack stands and get it back outside. Having the wheels painted now.


1983 CD
 

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77 280E, 78 450SEL, 86 300E, 87 300E, 90 300E, 92 400E & 4 scooters
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233 Posts
OMG, the video sounds just like a tractor engine should.

Hell, I mounted a coffee can full of marbles to my A/C compressor just to make sure racer boy with 1000 watts of stereo could hear me commin : )
 
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