When should the precombustion chambers come out?

The reason for asking is that the reconstitution of my dear governor has lead me to remove the injector pump housing, the fuel transfer pump and so on up to taking the injector valves out to get tested. So when I look down in those holes, I wonder if its a good time to stop....?
If the injector valves are cleaned or replaced, is the job still just half done without attention to the pre chambers? Is there anything that can help short of removing them (pre chambers)?

Appreciate thoughts from those who know.

My opinion only....Leave them alone unless you know you have a problem or you are going to take the head off. I have removed some on a parts engine and took the threads off of the chamber as they came out. Didn't do the head threads a whole lot of good either. The standard chambers aren't a big investment, but fixing the threads in the head is pricey.

The older 2 piece style chambers can be resealed at the top without removing the main piece if you have the correct tools.

CCJ,
Have no reason to believe that there is a problem with the pre chambers, so will just leave them be.
Was concerned that the new or cleaned injectors would not show improvement in combustion if the pre chambers could 'hold them back' . Thanks for the opinion.

The real problem wih chambers is coolant leakage from the metal gasket under the threads where it screws into the head.When these go then compression gets into the cooling system and causes all kinds of problems and esp. if setting can leak coolant down on top the pistons.There are a couple other problems that can take place but this is the main problem.I remember some of the one piece chambers had a serrated top on them where the two piece was just a cast iron or steel top half above the head.Can,t remember if all the one piece had the serrated top or not, been too many years since I worked on them.

One item not mentioned and a key item for pre-com chamber life is the maintenance of the cooling system. Chambers seem to last forever if corrosion on the water side is controlled but many die from corrosion pin holes clear through the chamber walls.

I'm a fan of the later one piece chambers where sealing 0-ring requirements are minimum......also available in the glow plug version to match your starter conversion if your up to a complete Cat design system.

As for timing of removal and replacement I would agree that it is probably best to disturb them when you have the head off for overhaul work.

As for testing nozzle capsules I'd get a quote for that service first as new capsules are pretty reasonable.

OM you are right that chambers can and do eat through the sides of them if the coolant isn,t protected (treated) with an inhibitor.I,m sure with the older or antique tractors they really need attention to this matter and try to eliminate all these problems with the older engines maybe negleted and also newer ones too.

Short of taking out the chambers, how do you tell if they are one or two piece?
There you go again, Ole' Magnet, tempting me to try another improvement!
Seriously though, the discussion of corrosion makes sense. Will make a note to address these chambers when, (and if) the head ever has to come off.
The capsules are about $50 each, so it may be worth checking the cost of checking the inj. valves.
Speaking of getting estimates...... With the injector housing off, what would you guys suggest in the way of preventative maintenance and checking for operation of the pumps????? Can it be 'adjusted' off of the machine?
yellerc@

It,s kind of hard to explain the difference of the one piece and two piece but by looking at the top and down into the nozzle hole you can tell as the two piece will stand out by looking.As for checking the inj. housing off it takes a special degree wheel and pointer and also the specific degree specs. for each cyl.I forgot to mention too that the top part of the two piece chamber has threads in it bigger than the nut that holds the nozzle and body in and it takes a large threaded bolt and a spacer to drop down in side the chamber threaded area to pull that top off and then the special splined bolt to remove the chamber itself.

I am currently replacing the pre chambers on my 70D grader with aftermarket chambers to accept glow plugs, the threads in the head didn't fare too well on two cylinders when i took them out. I purchased a helicoil set to renew the two holes that were damaged. It is 1.125 diameter w/12 threads per in. the set includes the drill,tap,installer, and new inserts. I am just now in the process of installing the helicoils. I will post again with results. This kit will probably be for sale in the soon future to anyone who might need to do some head repair.
Thanks
Vernier

Checking the injection timing and adjusting the lifters to spec is best done with the injection pump housing installed on the engine so any wear in the timing gears is accounted for. I'm sure when installed on a new engine, one adjusted to spec with the degree wheel will perform perfectly, but on an old engine, it probably will lag the spec some.

If your flywheel isn't installed correctly, so the TDC marks line up, then it might be sort of time consuming to do it properly with the housing installed on the engine. If you have to, there's a procedure to re-establish the marks that's detailed in the serviceman's reference book for the D318 if yours are off. Not necessary to pull the flywheel to fix it unless you have it off for some other reason.

On the one piece chambers.........All of them I have seen stick up out of the head a little more than the 2 piece ones. Inside there will only be one diameter of internal threads (for the injector hold down nut).

On the two piece chambers, if you look down inside, you should see 2 different thread diameters there. The first one inside the hole is larger for the removal tool for the top part of the chamber to screw into. Then on down in the main part of the PC chamber there is the smaller thread for the injector hold down nut.

Look at this thread about the D2 chambers. OM has some pictures on there of the different types. As you should be able to see, the 2 piece style has a separate "hat" that's sealed onto the main piece with an o-ring seal in addition to the one on the outer diameter that seals against the head and the copper or soft steel ring at the bottom where it screws into the head.
www.acmoc.org/ACMOC_BB/showthread.php?t=...recombustion+chamber