Richard took #2 and 3 Injectors and had them tested. They are good. They were just replaced in the beginning of October. He did change them around and I think there was no change in one cylinder when he opened the injector, can't recall which one. I had a used engine that I purchased from ASAP Motors in Houston dropped in at the end of February this year. Engine cranks right up when cold 20 degrees without block heater plugged up and she uses very little oil. The old engine consumed huge amounts of oil and and was very hard start in cold weather. I had to use the block heater. This leads me to believe that the engine is good. Is there something else other than a complete rebuild of IP if one cylinder is bad on IP. Was told by independant MB mechanic that cylinder 2 and 3 are weak. This rough idle is just too rough! Thanks for any input

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Thanks,
T.C.
1979 300D non-turbo silver

I was doing some casual reading of a new book I just purchased, the Haynes manual for "Mercedes-Benz Diesel 123 Series"... so let me quote you from it's troubleshooting section for the likely causes for this symptom:
(1) Air filter clogged,
(2) Fault in the fuel injection pump or timer,
(3) Clogged fuel injector,
(4) Leaking head gasket...,
(5) Timing chain worn,
(6) Camshaft lobes worn, AND
(7) Contaminated fuel.
Q - What do you suppose is meant in (2) where it says "... or timer"?
Regards,

Isn't the IP timed?

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-justin

1987 300TD, 1987 300TD
2008 R32, 2000 Passat Wagon

I just remembered, these Haynes manuals usually have a section titled "Use of English" that serves to translate "English" to "American"... but NO, they don't show "timer". Maybe it was a "typo"!
Sam

As you suggested, Jimmy L., We switched injector 1 and 4. There was still no change in the idle in the #4 cylinder. What would be the possible culprit of that cylinder not firing? Thanks!

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Thanks,
T.C.
1979 300D non-turbo silver

Have you done a compression test? How did you confirm that #4 was the problem?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

We pulled the head and both #4 Cam Lobes are worn. At this point, I guess it is...replace the Cam Shaft! This was on a list of possible culprits posted by Samuel Ross addressing this post. No, I have not done a compression test. Engine does not use much oil and starts right up, never using the block heater. We eliminated it being an injector by doing what Jimmy L suggested...when you bleed the #4 injector there was no change in the idle. There was a change in all of the other injectors. We switched #1 and #4 and the problem was still in #4 indicating a problem with the cylinder. I am hoping the worn cam lobes are causing the rough idle and not the IP. Thanks!

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Thanks,
T.C.
1979 300D non-turbo silver

Wasn't 1979 the last year where some of the cams would wear due to inferior metals used???? Seems like I remember this being an issue with some W116's.
However, memory is not my strong point.....

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

I posted a new thread Camshaft 1979 or 1980-81. What year did MB start with Pencil glo-plugs? I have pencil glo plugs. Any ideas?

__________________
Thanks,
T.C.
1979 300D non-turbo silver

On my previous 300DT (an 85), I chased every possible cause of the rough idle to no avail, although all these things are important for good engine performance...

1) injectors ...bought new ones and before installing, brought them to a shop and had the release pressure and spray pattern checked, all OK...installed to torque spec. with new crush washers

2) compression...all cylinders tested within 310 to 350 psi

3) timing (start of fuel delivery)...adjusted using drip tube

4) new timing chain

5) cleaned banjo bolt and line off of manifold

6) cleaned injection valves on top of IP and replaced copper seals

7) adjusted rack damper on IP (adusted all the way in, with no effect)

8) adjust idle speed (I think somewhere between 750 and 850 rpms)

9) adjusted valve clearances

10) new engine mounts, transmission mount, engine shocks

In the end, and after lengthy discussion with a guy from a company that rebuilds injection pumps (vary candid, no BS), I concluded that the notorious rough idle common to almost all of the 123 5 cylinder diesels, is caused by IP. This is a very complex (ingenious) mechanical device that will wear over time and go out of calibration, resulting in noticable symptoms (rough idle) after a few hundred thousand miles. Rebuilding involves replacement of various parts (sleeves, plungers, seals, rings, etc..) finished by bench calibration. At high speeds, the slight variation in fuel delivery characteristics between cylinders is not noticable given the total volume of fuel delivered, but a idle, these differences become more significant and result in rough idle. If you can live with the rough idle (easier said than done!) these engines will still perform admirably at higher rpms for many more thousands of miles ....just avoid stopping at red lights and such!

That said, my second 300D (84 wagon), had real bad front end shake at idle (if I set a glass of water on the dash, water would splash out), and when I adjusted the rack damper in, the idle smoothed right out (engine still rocks a little), but at least the front end isn't doing the Irish jig. What really fries me about these cars is the rough idle in combination with the design of the air filter housing....on both of my cars, I replaced and/or welded broken air cleaner mount brackets a few times!!!!! Damn, that is a pain!!!

Perhaps someone can comment on inherent characteristics of 5 cylinder turbo engines vs. 4 cylinder (240Ds) and 5 cylinder non turbos....I have seen a few nice 5 cylinder non turbos and 4 cylinder cars at idle, and they seem to purr with a nice evenly spaced clatter (music to my ears). The 5 cylinder turbos all seem to have that characteristic dink, dink, dink, dink. I don't buy the argument of the odd number of cylinders causing an imbalance...that seems kinda dumb to me...but I heard from someone that the turbo has an impact...I just don't know enough about how inherent engine design features result in performance characteristics.

Mark

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

I had already priced having the IP re-built, but had still not pulled the valve cover. Mr. Ross posted on this thread stated that that was 1 of 7 things that would be the likely culprit of the rough idle. We had put in new engine mounts and injectors. My 300D is a non-turbo so it does not have a rack dampener pin. Will post if the cam shaft solves the problem

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Thanks,
T.C.
1979 300D non-turbo silver

... assure you that IF my previous POST [ #19 above ] you refer to turns out to lead you to the proper solution... PLEASE DO NOT anyone think I'm anything but lucky and that my suggestion was purely coincidental.
I just had read this new reference I had purchased!
Regards,