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  #1  
Old 11-29-2004, 04:04 PM
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Should I clean my prechambers too?

Forgive my inevitable stream of conciousness here I tend to think alot while typing.

I've been experiencing a strange power loss on my wifes '83 300D. This car has been converted to WVO and the power loss is most noticable when running on WVO. On Diesel the car won't top 80. On WVO it won't go past 50. I'm assuming there is a leak or many leaks.

I have replaced both the pre and primary fuel filters.
I have replaced the lift pump gasket and the primer pump.
I have replaced the injector return lines.

As you can see by the attached photo the appears to be a leak around the back 3 injectors. I'm not positive that the leak wasn't originally from the return lines. Since they were pretty much toast. Based on what I can gather there very well may be a ton of this gunk down in the prechamber above the heat shields. Of course this stuff could also be oozing up from there as well.

Is there an easy way to clean this when I pull the injectors? Or would it be best to pull the prechambers out to clean them?

On another side but related note, does anyone know where I can get some narrow (think detail paintbrush) brushes that are either brass or stainless steel? I've tried removing that crud from around my injectors but I am affriad of really messing something up by scraping it off with a screwdriver or awl and I can't get a standard wire brush in there.

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Should I clean my prechambers too?-injectors2.jpg  
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'84 300CD Turbo 132k (Anthracite Grey) - WVO - My daily driver - Recently named coo-coo-coupe by my daughter.
'84 300D Turbo 240k (Anthracite Grey) - Garage Queen
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I'm not a certified mechanic, but I did stay at a HolidayInn Express last night.
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  #2  
Old 11-29-2004, 04:35 PM
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Try some carb cleaner in the prechambers and injection nozzles. Try an old toothbrush with the bristles trimmed short. I doubt you'll hurt anything with nylon bristles. If you use carb cleaner in the prechambers, try to suck out the crud before you blow it out and make sure you don't put a lot down into the combustion chamber. You don't want to damage anything. If the glowplugs come out, it will be MUCH easier to clean the prechambers, but still no picnic
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  #3  
Old 11-29-2004, 05:02 PM
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WVO has less BTUs then diesel so if your having trouble pushing 80 on diesel then i would not be suprised that you are down on power. The motor has some other problems like maybe low compresion or timing is off.
WVO will clean the carbon up very nicely all by itself, it is a great decreaser. I have heard of people running B100 with a cloged intake and within 2 tanks the intake will start to clean itself(as long as the egr is hooked up and working).
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  #4  
Old 11-29-2004, 06:10 PM
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Quote:
Originally Posted by JamesStein
On another side but related note, does anyone know where I can get some narrow (think detail paintbrush) brushes that are either brass or stainless steel? I've tried removing that crud from around my injectors but I am affriad of really messing something up by scraping it off with a screwdriver or awl and I can't get a standard wire brush in there.
You might try checking at Micro-Mark and searching on the keyword "brush". One of the items you'll find is this "mini brush with brass bristles". The bundle of bristles is about 4 mm in diameter. Note that refills are available, and that a similar brush is available with fiberglass bristles.

The brass one I bought from them a few years ago was of German manufacture, and looked just like these.

Micro-Mark has all sorts of freaky little stuff, like several different sizes of ear polypus. Freaky, but useful.
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  #5  
Old 11-29-2004, 07:16 PM
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Thumbs up Brass Brush

I used a 12 gauge shotgun cleaning brush. These can be purchased for less than $3.00 at any Wal Mart. Buy brass, not the nylon ones.
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  #6  
Old 11-29-2004, 07:22 PM
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It is my considered opinion from reading the paper Mercedes Factory shop manual.... and understanding some of the physics.... that you absolutely must take the precombustion chambers out to clean them....
Those are very small holes.... drilled radially... and very important because if they , or even one, are clogged then no matter how well your injection nozzles are working your fuel spread is shot... multiplied 2000 to 4400 time per minute it really adds up....
Those holes are at the most important interface of all that happens inside your engine... critical.... to performance... and fuel mileage...
Taking them out will give you a chance to put new compression washers where you need them as you put it all back together... always use new ones...
One thing I would try, since it is cheap, is to run Diesel Purge , ACCORDING to INSTRUCTIONS... this has helped a lot of owners here on the forum...
total cost for two cans... like $20... and I would run two cans through it....
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  #7  
Old 11-29-2004, 07:26 PM
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Do not stick anything into the pre-chamber to clean it, you risk breaking the ball pin sitting under the nozzle, and replacement requires removing the pre-chamber.

Unless you have glassy carbon in there, cleaning won't do you any good as the soot is normal, and abnormal amounts are injector, compression, or timing problems that will clear when the problem is fixed.

I would suspect you have leaking suction lines and/or a plugged tank screen -- you are using a separate heated tank for WVO, aren't you? If not, you will have terrible problems with fuel delivery to the IP, it's too thick. Air getting in will greatly reduce power and top speed, and eventually you will end up with a no start condition (this is a real PITA, too!).

Inspect the fuel lines for fuel residue. If the line between the lift pump and the standpipe is wet, it's probably leaking air in -- you will see a stream of bubbles running into the main filter (a large bubble bouncing around is normal, air going to the main filter is NOT).

If the priming pump has to be pulled up hard, you have a restriction in the fuel lines or tank scree.

You should also check the chain stretch and injection timing -- replace the chain if it has more than 8 degrees stretch (a search will get you the procedure).

Peter
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  #8  
Old 11-29-2004, 07:42 PM
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Have you checked the boost aneroid (alda)? I had similar problems not long ago and found that the housing leaked considerably. I eventually ended up using a non-hardening sealer between the two halves to obtain a decent seal.

Also, the other thing that helped considerably on power was a valve adjustment.

Are you getting any kind of nailing? I would think nailing would be very noticable if the prechambers or injectors had a problem.
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  #9  
Old 11-29-2004, 08:29 PM
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Quote:
Originally Posted by leathermang
It is my considered opinion from reading the paper Mercedes Factory shop manual.... and understanding some of the physics.... that you absolutely must take the precombustion chambers out to clean them....
Makes sense to me. Thats what I was thinking.
Quote:
Originally Posted by leathermang
One thing I would try, since it is cheap, is to run Diesel Purge , ACCORDING to INSTRUCTIONS... this has helped a lot of owners here on the forum...
total cost for two cans... like $20... and I would run two cans through it....
Forgot to mention I've run a purge on it. To be honest I'm not thinking that they are dirty and need cleaning. More like the heat shields are either missing or worn and leaking.
Quote:
Originally Posted by SD Blue
Also, the other thing that helped considerably on power was a valve adjustment.
Are you getting any kind of nailing? I would think nailing would be very noticable if the prechambers or injectors had a problem.
I did adjust the valves the other day, you can probably see by that picture that I had the vavle cover off. Didn't make any difference power wise, just made the engine run a little smoother. It still nails a little.
Quote:
Originally Posted by psfred
I would suspect you have leaking suction lines and/or a plugged tank screen -- you are using a separate heated tank for WVO, aren't you? If not, you will have terrible problems with fuel delivery to the IP, it's too thick.
I do have a 2 tank setup. Right now its not heated. But I don't think thats the root of the problem. My 300CD is setup exactly like the 300D and when the WVO is too thick due to the cold my 300CD actually stutters. This is just a loss of top end power.
Quote:
Originally Posted by psfred
Air getting in will greatly reduce power and top speed, and eventually you will end up with a no start condition (this is a real PITA, too!).
Inspect the fuel lines for fuel residue. If the line between the lift pump and the standpipe is wet, it's probably leaking air in -- you will see a stream of bubbles running into the main filter (a large bubble bouncing around is normal, air going to the main filter is NOT).
This is what I suspect. I've cleaned all the lines around the IP. And tried to clean around the injectors. There is seepage at some of the injector lines on the IP and around the 3 back injectors. New o-ring and such are ordered for those lines. There is no air getting into the lines from either the WVO tank or the diesel tank. I've got clear lines running to the lift pump and see no bubbles coming into the pre-filter. So whatever air leak there is is around the IP.
Quote:
Originally Posted by psfred
You should also check the chain stretch and injection timing -- replace the chain if it has more than 8 degrees stretch (a search will get you the procedure).
When I did my valve adjustment I tried to do the simple quick check of chain stretch. But I never could find the index mark on the camshaft. One of these days I'll get a dial gage so I can do that properly.


I've never pulled an injector on one of these engines so perhaps my understanding is flawed. But looking at the design it appears that there is a gap between the injector and the prechamber at the surface. Since the 'seal' ie heat shield/crush washer sits at the tip of the injector. Unlike a sparkplug where that seal is above the threads. I want to remove the injectors and replace the heat sheilds. I'm afraid that the gunk I see on the top of the prechamber is going down into the threads. I don't want to accidently push any of that stuff into the prechamber when putting new heat shields in or reinstalling the injectors.
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'84 300CD Turbo 132k (Anthracite Grey) - WVO - My daily driver - Recently named coo-coo-coupe by my daughter.
'84 300D Turbo 240k (Anthracite Grey) - Garage Queen
'83 300D Turbo 220k (Orient Red) - WVO - Wifes daily driver

I'm not a certified mechanic, but I did stay at a HolidayInn Express last night.
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  #10  
Old 11-29-2004, 09:33 PM
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Good post....
Glad you could not find the marks on the camshaft because the FSM REQUIRES, when there is ANY performance complaint.... (and you certainly have THAT.... LOL....) that the movement of the number one valve be used to check chain stretch...
On one MB engine the factory increased the size of the holes in the prechamber , changing nothing else, and it made several horsepower difference in the engine... proper fuel dispersal is key to power and economy... many people visualize the action in the bore as causing movement outwards from the bore area.... and hoping that keeps the preC holes clean...but at the time of the explosion caused by the (hopefully ) vaporized fuel... more area is in the preC than the bore... so the pressure can be high there with no movement... then the decrease in pressure happens with the power being used to move the piston down... once something like soot or something mechanical like broken glowplug tips... or carbon from the glowplug area gets into the hole area it really has no place to escape to....
All this is just conjecture on my part..... LOL
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  #11  
Old 11-30-2004, 06:18 PM
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There is a notch in the thrust washer on the cam sproket -- line that up centered on the small bump on the front cam tower (at about 1:30 -- just to the left of the top). Then read the balancer degree wheel pointer. This will be close enough to tell you if the chain is off. I would NOT use this method to caclulate or install and verify offset keys to get the cam timing exact, it's not close enough for that.

Dollar to a donut it will read more than 8 degrees ATDC.

Injection timing will be similarly late, but don't adjust it until you have a new chain in, or you will have to do it again.

Late timing makes these engines pretty wimpy, and will eventually reduce top speed, along with copious smoke.

Bad injectors will do the same, and make the late timing symptoms worse.

Minor seepage at the injectors is normal, if a pain, but if you get bubbles while it's running, you need new seals. Make sure they are in right side up!

Torque is 50 ft/lbs, one pull. The correct 27 mm deep socket is available at Sears.

Peter
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1988 300E 200,012
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1985 Volvo 740 GLE Turobodiesel 218,000
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  #12  
Old 11-30-2004, 08:13 PM
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Don't forget to check the throttle linkage as well.
Have someone sit in the car and put the throttle pedal to the floor as you look to ensure the linkage is to the stop on the injection pump. I have seen many cars that were up to 3/4 inch off and cured their "low power" problem simply by getting them full throttle. If there is any gap there, it is like a governor and limits the potential output considerably.
Good luck, Adam
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  #13  
Old 12-01-2004, 12:34 PM
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Leather,

How do you get the engine speed up to 8,800 RPM the get the injectors squirting 4,400 tmes per second?

P E H

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