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  #1  
Old 03-12-2006, 12:11 AM
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pre combustion chamber servicing

how important is it,or how often would one need to service or de carbon the pre combustion chambers? This looks like a pretty intense job. Just looking for ways to improve starting and overall driveability.
while i was trying to fix my last problem ,i noticed that my chamber was very sooty,i guess it is a diesel,but is that OK? can you reuse an old chamber or do you need to replace them? what tools and techniques are required?

Last question, i understand the theory of the PCC, but what is the purpose of the little steel ball that appears to be at the bottom of the chamber?

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1980 mercedes euro 300D 232000 miles(died,now parts car)
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Old 03-12-2006, 10:58 AM
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Greg...where are you
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Old 03-12-2006, 11:34 AM
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Drive the car hard and don't worry about it. Carbon build up is only a problem with a lot of low rpm around town use.

Just inspect them and make sure the balls are not lose. If they are they are pretty simple to replace. You just need a special socket to yank them.
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Old 03-12-2006, 11:35 AM
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Quote:
Originally Posted by wade
how important is it,or how often would one need to service or de carbon the pre combustion chambers? This looks like a pretty intense job. Just looking for ways to improve starting and overall driveability.
while i was trying to fix my last problem ,i noticed that my chamber was very sooty,i guess it is a diesel,but is that OK? can you reuse an old chamber or do you need to replace them? what tools and techniques are required?

Last question, i understand the theory of the PCC, but what is the purpose of the little steel ball that appears to be at the bottom of the chamber?

First of all, I'm no expert when it comes to working on PCC's. However, the SD had the head removed and replaced and the PCC's had to be removed to accomplish this. They have a locking ring at the top that is removed with a special tool for this and the chamber itself is pulled with a slide hammer. They get locked in there pretty good over the years and quite a few blows are required to get them to release.

You can reuse the old PCC's if they are in good shape, however, after 180K on the SD, the shafts that hold the ball were loose in the side of the housing........thereby running the risk of losing the ball at sometime in the future. So, I elected to have the shop install new PCC's.......$60. per.......

The steel ball is involved with the distribution of the fuel in some fashion. Without it, the cylinder will present all kinds of issues including knocking. It does seem like a device that was added at the last minute to solve a specific problem with the PCC.......but........who knows?

The PCC's that were removed from the SD were not packed full of carbon, however, some of the holes at the end of the PCC were blocked and needed to be cleaned if they were to be reused. As mentioned, I decided to simply replace them.

The performance of the 617 has improved dramatically since the head was installed. Instant starts at all temperatures. However, new exhaust valves and all new seats could also be part of the benefit.

If it were me, I probably would not go through the effort to simply remove the PCC's. If you were considering a valve job, naturally, they will be removed at that time to check the flatness of the deck. The decision to replace them or reuse them can be made after removal. If you are going to keep the vehicle for quite a long time........replacement is probably the best idea.
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Old 03-12-2006, 09:22 PM
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great info thanks guys.................hey stevo, who's Greg??????
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1980 mercedes euro 300D 232000 miles(died,now parts car)
2004 2500 ram cummins diesel
1980 harley shovelhead
1988 anniversery corvette zr1(engine)
1978 240D 4spd 240000 miles (new benz toy)
1946 Cessna 140, Continental 0-200
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  #6  
Old 03-12-2006, 09:26 PM
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Quote:
Originally Posted by wade
great info thanks guys.................hey stevo, who's Greg??????
........."Leathermang".........
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  #7  
Old 03-12-2006, 09:27 PM
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The om617 injectors shoot their fuel as a tight jet. This jet then strikes the ball and atomizes.

As far as the soot is concerned, it may actually improve performance. It acts as an insulator to keep heat in the combustion gasses from escaping to the walls. So long as the soot isn't too thick or plugging anything it shouldn't be much of a problem. While scanning another diesel forum for another type of engine, I came across one guy who had his prechambers and piston heads ceramic coated to try and squeeze every last bit of power out of his engine. After spending $500 he never did say how it worked.

I think the only real critical thing on the prechambers to wear out other than the ball that Brian mentioned is the holes in the bottom. They can crack or just erode. If this happens the jets of combustion gasses may hit the walls of the cylinder, the piston, or the head. This results in a loss of power and can result in damage.
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Old 03-12-2006, 10:35 PM
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Quote:
Originally Posted by Brian Carlton
........."Leathermang".........

Right..he would always chime in on a "pre chamber thread" , guess hes busy on the farm

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Last edited by Brian Carlton; 03-12-2006 at 10:51 PM.
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