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  #16  
Old 08-10-2015, 11:57 PM
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Last edited by Left Coast; 08-11-2015 at 12:00 AM. Reason: redundant
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  #17  
Old 08-12-2015, 08:05 AM
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Quote:
Originally Posted by leathermang View Post
Here is the problem with trying to blow it out with piston movement....
The glow plug hole is 90 degrees to the precombustion chamber and the only access to the precombustion chamber is via approximately 7 radially drilled holes at the bottom.... meaning in a plane parallel to the top of the piston.....because that is where the fuel spray needs to be put when the engine is running...
You can not get enough air flow power to count on blowing out loose pieces of carbon...
So, too many 90 degree turns....and too small an access to the air connected to the glow plug hole...
There might be a reason it was not in later FSM's.....
Either use heavy grease to capture the carbon or take out the injectors and blow out from that side...
The section of the Mercedes Manual on CD that covers my 84 300D has no front end alignment specs in it. And, when you look at the printed Chassis Manuals you find that there is a whole lot of stuff missing on the CD that is in the Manual.
So that is my explaination for the missing part of reaming the Glow Plug proceedure; it is missing because they did not include it on the CD just like they did not include the other missing stuff.
When I find My Printed copy of the Turbo Diesel Manual I will look it up.

Keep in mind that carbon getting into the Cylinders is no worse for a 617.952 then it is for the 240D Engine. So I don't see any reason they would purposely drop the Instruction on the 617.952.

As far as the blowing out issue goes if you are cranking the Engine with the Starter when the Piston is coming up on the compression stroke; due ti the small holes causing a restriction there is going to air pressure created inside and the air that goes through the holes is under pressure and is going to created turbulance (if you don't believe that read how a pre-combustion chamber works) and the air is going to go through those holes at a high pressure.
And, that is what is going to blow out the carbon.

If any carbon sticks to the Prechamber due to the Fuel being Injected and stays. When you start the Engine the violence of the Combustion is going to take care of it.
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  #18  
Old 08-12-2015, 09:18 AM
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Who said anything about worrying about carbon getting into the combustion chamber ?
Not me.... looks like you are the one that needs to read up on how the pre combustion chamber is built and works.
I am concerned that loose carbon released by reaming the glow plug holes will fall into the bottom of the pre combustion chamber and interfere with the effective spraying of the atomized fuel into the combustion chamber through the very small... approx 7 holes, it differs over time as does the size of those holes, which spread the fuel into the hot air of the combustion chamber.
Those holes are basically flat drilled level with the top of the piston and ( looking in from the combustion chamber ) pointed at the center of the pre combustion chamber..
So turbulence , YES, effective air flow up and out of a 90 degree turn going out of the glow plug hole , NO.
In fact, if you understand cyclonic vacuum cleaners or old style Oil Bath air cleaners.. which , if the oil is clean, have the potential for catching much smaller particles than a paper element filter, you would be able to visualize those pieces of carbon being thrown against the top of the pre combustion chamber...past the glow plug hole due to their mass.....and being caught in an endless loop... with the lighter air making the turn out the glow plug hole.
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  #19  
Old 08-12-2015, 09:21 AM
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I did more checking in the Mercedes CD Manual set and there is no instructions at all listed in the 1982-1985 300D section on removing and replacing the Glow Plugs.
What is there is in the Engine Electrical System area.

The pic is a screen print of the part of the index with the Glow Plug info.

I could not find the removal and install of the Gloe Plugs in the maint. section either.

I am wondering what is in the Mercedes EPC?
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Glow Plug Reaming-glow-plug-section-cd-manual.jpg  
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  #20  
Old 08-15-2015, 07:53 AM
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^ I looked in the '77 year button and found the item below.
Attached Files
File Type: pdf glow plug r&r, early:15-515.pdf (116.8 KB, 38 views)
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  #21  
Old 08-15-2015, 03:07 PM
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When I reamed my glow plug holes, I used a vacuum cleaner to suck on the holes and then I spun the engine over to blow anything else out. The Carbon is such a fine powder I feel it would be silly to even worry about it. These engine go 300k miles without needing the combustion chamber or precup cleaned of Carbon, and that's enough to not worry. If the powder did fall in, blowing it out is easy. If it doesn't get blown out, it'll either be burned in the prechamber or blown into the combustion chamber and out the exhaust valves. The burning gas coming out of those prechamber holes is EXTREMELY hot and fast. Any chunk of Carbon that got stuck in a hole would be flame cut and evaporated into nothing within minutes. If you're a shooter, you know that Leading in revolvers is caused by an undersized Lead bullet that is flame cut by burning gases and deposits molten Lead in the forcing cone and cylinder throats. The Carbon wouldn't stand a chance.

Also, if the soot went straight up when spinning the engine over to blow it out, it would hit the pintle ball's flat underside and be directed out the side glow plug hole by the air current.

Grease, no grease, colloidal Gold, I don't think it matters what you put on the reamer.
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  #22  
Old 08-15-2015, 03:50 PM
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Manny, I fine collection of imagination and fiction.
Do you understand that Carbon is an element ? You can not burn it... it can be "burned" in Stars...
' fine powder' ... you are assuming that a none of the carbon breaks off in pieces.. absent grease to catch it.
Do you know the actual size of the holes in the precombustion chamber ?
" Also, if the soot went straight up when spinning the engine over to blow it out, it would hit the pintle ball's flat underside and be directed out the side glow plug hole by the air current." -manny
You probably have never seen an oil bath cleaner... or certainly do not understand the physics behind them.
Where do you get the ability to say that our diesels usually go 300 k without needing precombustion chamber hole cleaning ? What is the recommended service interval for the precombustion chamber and why ?
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  #23  
Old 08-15-2015, 04:26 PM
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Quote:
Originally Posted by leathermang View Post
Who said anything about worrying about carbon getting into the combustion chamber ?
Not me.... looks like you are the one that needs to read up on how the pre combustion chamber is built and works.
I am concerned that loose carbon released by reaming the glow plug holes will fall into the bottom of the pre combustion chamber and interfere with the effective spraying of the atomized fuel into the combustion chamber through the very small... approx 7 holes, it differs over time as does the size of those holes, which spread the fuel into the hot air of the combustion chamber.
Those holes are basically flat drilled level with the top of the piston and ( looking in from the combustion chamber ) pointed at the center of the pre combustion chamber..
So turbulence , YES, effective air flow up and out of a 90 degree turn going out of the glow plug hole , NO.
In fact, if you understand cyclonic vacuum cleaners or old style Oil Bath air cleaners.. which , if the oil is clean, have the potential for catching much smaller particles than a paper element filter, you would be able to visualize those pieces of carbon being thrown against the top of the pre combustion chamber...past the glow plug hole due to their mass.....and being caught in an endless loop... with the lighter air making the turn out the glow plug hole.
It really isn't atomized fuel passing through the 7 holes in the prechamber is it? I've always understood it as the atomized fuel enters the precahmber and under the pressure and heat of 22-1 compressed air it ignites or begins to ignite and then that (rapid oxidization)burning more or less explodes out from the prechamer (where the explosion is initiated) and that exploding mixture of atomized fuel and o2 flows out ever expanding into the larger combustion space atop the piston and because it occurs ATDC it exerts the downward pressure on the movable piston which through the connecting rod and crank converts that force into rotational motion.

If it was the case that simply atomized fuel was exiting the prechamber there would be no carbon from combustion in the prechamber.

I don't know the exact word used to describe the ignited, exploding and expanded fire ball that first exists in the prechamber that ultimately enters the space above the piston, but it is much more than simply atomized fuel.
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  #24  
Old 08-15-2015, 05:06 PM
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Greg,
Of course Carbon is an element. Do you know what "burning" means? It refers to a redox reaction specifically, usually to oxidize. Oxidizing refers to adding Oxygen to the element in order to make an oxide. Carbon Dioxide. Carbon Monoxide. Understand? When temperatures are high enough, Oxygen will react with PLENTY of elements including Carbon.

I honestly don't know how you got on that little path to fallacy. Elementary education teaches us about elements and burning. BTW, Carbon is FUSED in stars massive enough to utilize the CNO chain process. I won't try to explain fusion yet since we're trying to understand burning at the moment...

Have you removed your prechambers for cleaning? What do those paper manuals you are always referencing on here say about prechamber cleaning? Curious minds want to know.
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  #25  
Old 08-15-2015, 05:15 PM
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BatteredBenz, it depends on the load at the time. At idle, the fuel quantity injected is very small and most if not all of it burns completely in the prechamber. It only needs enough fuel to keep the engine freewheeling at 750 rpm. As the piston moves upward, it pushes the air up into the prechamber. This current of air enters through the holes and swirls around inside the prechamber. At full load with max fuel being injected, the burning begins in the prechamber. The burning mixture creates pressure and blasts out through the holes into the combustion chamber. The turbulence created mixes the injected fuel very well with the air charge, and the result is quieter operation and better burn. The prechamber face looks like a rocket engine in that stage. The pintle ball is what creates the swirl as the air enters the prechamber and it's what helps the injected fuel spray break up and mix with the air within the prechamber.

Also, the word you're looking for is "deflagration." The mixture deflagrates within the cylinder. That word means to burn quickly. It doesn't explode per se, but it does burn very rapidly and that's what gives you the diesel knock.
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  #26  
Old 08-15-2015, 05:35 PM
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Quote:
Originally Posted by mannys9130 View Post
BatteredBenz, it depends on the load at the time. At idle, the fuel quantity injected is very small and most if not all of it burns completely in the prechamber. It only needs enough fuel to keep the engine freewheeling at 750 rpm. As the piston moves upward, it pushes the air up into the prechamber. This current of air enters through the holes and swirls around inside the prechamber. At full load with max fuel being injected, the burning begins in the prechamber. The burning mixture creates pressure and blasts out through the holes into the combustion chamber. The turbulence created mixes the injected fuel very well with the air charge, and the result is quieter operation and better burn. The prechamber face looks like a rocket engine in that stage. The pintle ball is what creates the swirl as the air enters the prechamber and it's what helps the injected fuel spray break up and mix with the air within the prechamber.

Also, the word you're looking for is "deflagration." The mixture deflagrates within the cylinder. That word means to burn quickly. It doesn't explode per se, but it does burn very rapidly and that's what gives you the diesel knock.
I can't disagree with much of what you've added but I will make note that although at a point air is pushed by the rising piston up into the prechamber through the small holes and causes swirling while doing so, fuel is injected after that point and in fact is injected ATDC when the piston is moving downwards affecting a vacuum pulling the formerly highly compressed air down and out of the prechamber along with the igniting atomized fuel/remaining air mixture with it.

It really is a contained, controlled, and directed low velocity explosion. I am familiar with the varying degrees of oxidation velocity having in my distant past worked with hyper velocity oxidation of explosives.
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  #27  
Old 08-15-2015, 05:40 PM
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No. The injection event occurs a few degrees before TDC. The diesel is injected in a very fine mist, however that mist needs time to absorb the heat from the hot air and evaporate into fumes. Liquid fuel does not burn, no matter if it's a gas engine or a diesel engine. The injection event occurs a few degrees before TDC, the delay until ignition occurs, ignition happens right as the piston is approaching TDC, and then the pressure spikes rapidly right as the piston begins to reciprocate which pushes it down on the power stroke. The injection event during full load overlaps. The fuel will begun burning as the last of the charge is sprayed into the cylinder.
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  #28  
Old 08-15-2015, 05:43 PM
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Quote:
Originally Posted by BatteredBenz View Post
It really isn't atomized fuel passing through the 7 holes in the prechamber is it? I've always understood it as the atomized fuel enters the precahmber and under the pressure and heat of 22-1 compressed air it ignites or begins to ignite and then that (rapid oxidization)burning more or less explodes out from the prechamer (where the explosion is initiated) and that exploding mixture of atomized fuel and o2 flows out ever expanding into the larger combustion space atop the piston and because it occurs ATDC it exerts the downward pressure on the movable piston which through the connecting rod and crank converts that force into rotational motion.

If it was the case that simply atomized fuel was exiting the prechamber there would be no carbon from combustion in the prechamber.

I don't know the exact word used to describe the ignited, exploding and expanded fire ball that first exists in the prechamber that ultimately enters the space above the piston, but it is much more than simply atomized fuel.
You got it. Lots of Elements can oxidize they just need the right conditions to do that.
Carbon must be one of them or you would not have CO2, or CO gasses.
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  #29  
Old 08-15-2015, 05:47 PM
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What have we learned. Blowing the Carbon out of the Cylinders by cranking the Engine after reaming the Glow Plugs is in some of the Official Mercedes Diesel Service Manuals.

Next doing that apparently causes no harm because it has been done for I don't know how long with no issues.

If you don't want to blow out the Carbon out of the Engine by cranking the Engine then don't do it.
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  #30  
Old 08-15-2015, 05:51 PM
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^ Agreed.

Most people here respond to questions with "if it was wrong/not necessary Mercedes Benz wouldn't do it/suggest it."
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