Issue with a MB 300D

Single Tank WVO systems and blending SVO WVO to thin it.

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Issue with a MB 300D

Postby Zulu » Tue Oct 07, 2008 12:09 am

Let me just set the scene. I am on my 2nd 300D, first one covered 50 000Km on WVO. Straight, with a FPHE, but starting cold on the oil and letting it heat when the car heated. Ambient temp is never really very low. 2nd car on 6000Km now. Have not had a single issue, the cars have run like clockwork and perfect.

THE ISSUE....

My Father bought a 300D and now after 12000Km, the car has started to develop a "Funny". It has the same setup as mine, with a FPHE and also runs on straight WVO. The problem is that the car runs fine, but sometimes when you stop and idle, it starts to miss. it then continues to miss untill you pick up the revs and then it is fine again. The problem is that it doesn't do it every time, just sometimes, and there is no billow of smoke when it "comes right" again.

Traced the miss to no1, by loosening the feed line to the injector, and the miss is the same.
So.... we changed no 1 injector.... still does it.
We cahnged the feed pipe.... still does it
Changed the little Feed Pump at the top of the injector pump on no1, still does it.

So, you clever lads, what can it be.

I have thought that it is possibly that my father is 76 and drives to slow, and there is a blockage in the pump. My cars have not been driven like racing cars, but suspect a tad more spirited than than his...

Some ideas please, because the next step is to remove the pump and have it overhauled. Would be a shame, because the car only has 230 000Km on the clock...
Living in Africa, Driving on the goodness of the Sun and the rain, and loving every Km of it!!

72000 Km on the greasy stuff already... Oh Africa.. such a nice place to live!!!
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Postby coachgeo » Tue Oct 07, 2008 12:40 am

try some Lubramolly diesel purge or Sea Foam?

borrow his car and do an Italian tune up on it.
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Postby Zulu » Tue Oct 07, 2008 12:43 am

coachgeo wrote:...borrow his car and do an Italian tune up on it.


Yep, that was my answer as well.... :D
Living in Africa, Driving on the goodness of the Sun and the rain, and loving every Km of it!!

72000 Km on the greasy stuff already... Oh Africa.. such a nice place to live!!!
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Postby Zulu » Tue Oct 07, 2008 4:47 am

Just had a look at my IP on an 84 NA engine and there is no rack bolt. My Father's car is a '77, can't look now, but will have a look tonight and see, but was this bolt only applicable to the turbo models or NA as well.
Living in Africa, Driving on the goodness of the Sun and the rain, and loving every Km of it!!

72000 Km on the greasy stuff already... Oh Africa.. such a nice place to live!!!
Zulu
 
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Postby SunWizard » Tue Oct 07, 2008 7:55 am

Check the compression, maybe #1 is low.
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Re: Issue with a MB 300D

Postby David » Sun Oct 12, 2008 2:09 am

Zulu wrote:THE ISSUE....

The problem is that the car runs fine, but sometimes when you stop and idle, it starts to miss. it then continues to miss untill you pick up the revs and then it is fine again. The problem is that it doesn't do it every time, just sometimes, and there is no billow of smoke when it "comes right" again.


This is exactly what my car does when one of the filters is blocked, usually the OEM filter. I also run a disposeable pape filter in place of the MB strainer but the issue you describe usually occours when the main filter is blocking.

I surmise this is caused by the pump not having sufficent pull at idle and then stepping up at higher revs.
If you have installed a new filter ( and I'm talking within days because I have hasd some block very quickly and inexplicably) and the problem still ocours, I would look at the pickup strainer in the tank and work my way back through the fuel system to the engine.

Given my own experience, It would seem to me the problem is fuel starvation of some kind.
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Re: Issue with a MB 300D

Postby mixelpix » Tue Dec 16, 2008 4:24 am

Zulu,

Sounds like the tank vent line needs to be blown out. Being that close to the ocean, it is all the more likely that your diesel tanks will suffer the "fuel fungus" - cladosporium resinae. If find this common on the West coast of the continental U.S. and when I work on friends Benz's in Hawai`i. Do you use a biocidal additive? If you haven't you might want to also check the tank screen filter for sludge and possibly drain, remove and clean the entire tank. Do you see a lot of goop when you change fuel filters?

Likely the '77 123 has the 722.118 transmission from the 115 chassis series. You might be seeing other anomalies of their product development. It wouldn't affect idle, but there is no vac modulator and if you ever lose reverse gear let me know. Easy fix most people pay $1,000's for. Back to the 61x engine:

All the fluids and filters have been checked (and I am assuming the ignition-charging system is working properly, belts are tight, engine mounts and shocks are in good condition, the air filter mounts are still rubbery and all the vac lines are properly attached and have been blown clean within the last 2 years and you religiously tighten the intake and exhaust valves within spec every 12.5Km and checking for timing chain stretch over 3 degrees, and you have upgraded all the rubbers in the fuel system from the tank neck gaskets thru the send/returns under the tank and in the block to the braided injector return lines) (.1I/.35E, likely IEEIIEEIIE? should still say inside the engine block) and you are getting a stumbly idle... If you replaced the braided injector return lines recently and didn't verify the part #'s with a Benz certified dealer, you might have the wrong size internal diameter lines. I have seen this introduce air and create a similar stumble.

If you have had the injectors replaced, were they balanced to within 5 bar of one another? Whether made in India or Germany, the die casts for their industrial production are the same Bosch products in either country and the Benz plugs are of the most excellent quality. According to their service and maintenance literature the factory delivers them balanced within 10 bar and the certified installer shims them within 5 bar. This is ESSENTIAL for smooth idles. If they are old nozzles, remove #4 and inspect the tip. If it does not snag the ridges of your fingerprints, replace all the nozzles. While it is out do a very very sloppy and quick compression test and make sure it is not completely out of whack. Note, false compression test readings are easy to acheive and for true internal health, get engine oil analysis and have a proper leak down test performed (if diagnosis warrants that cost).

Hmm, yeah - blow some compressed air into the tank vent. While you are in there, remove the first aid kit holder and open up thetop of the tank. Remove the fuel send transmitter tube and inspect that for an accurate guage of the internal tank sludge factor. If your fuel guage is bouncy or non-working, this is likely where to fix it. If you dismantle the tube, just go slowly, the wires inside which guide the float and determine the resistance/level send are very brittle and will easily snap. If yours is or gets broken they are very swappable between different M-B makes/models.

Best,
-Patrick
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