I am working on a d4 that has had a rough life, I just put new valves and ground and fit the seats. This engine had new liners and ring about 900 hours ago and shows no wear in the cylinders. This engine misses on no 2 cylinder, I took the fuel pump apart tonight and reset the lifter height and installed a new injector in no 2 and reassembled everything and fire it up and still a miss on no 2, The only thing left is the precombustion chamber. Has anyone ever seen a precombustion chamber carboned up to the point it will not work right. This engine was ran many hours with a very bad valve in the no 2 cylinder also. Ron Meeder

No, but I suppose anything is possible.
Try moving the injector pump to another cylinder....may have a bad pump or check valve.

Hi Team,
yes, I have encountered this in an old D8 (D13000) engine being used to pump water. It was the only time though.
The customer sent the fuel pump and injectors for reco. as the engine was down on power.
The pump was ok, but two injectors were atomising poorly.
After reco-ing the injectors the engine did not run much better. After some discussion it was suggested that the pre-com's. be checked and 2 were found to be carboned up to about a pencil dia. hole through the carbon build up.
Cleaning out the chambers worked wonders.
Cheers,
Eddie B.

Any idea of how to go about cleaning the pre cup of the carbon?
I will be taking this a part in the pm and would like any ones ideas , soapy water disolves diesel carbon but takes time , what else works faster?
Ron Meeder, thanks for now.

I've burned the carbon off and out of automotive heads with an oxy-acetylene torch, but as far as how it would work to clean the precom chambers I don't know. If you want to try it, adjust the torch for a slightly oxidizing flame, touch the flame to the inside of the chamber and hit the oxygen lever. Be careful if you try this. .burning bits of carbon will fly all over the place!! Do this ONLY in a place where you might do arc welding or burning due to the possibility of starting a fire!! Also, do NOT keep this going for more than a few seconds or so at a time, letting everything cool back down to body temp between tries. Wear safety glasses plus a face shield, not to mention body protection. Bits of burning carbon will fly about as bad as air-arcing welds.

This method is probably going to be highly controversial. As the precups are steel, heating 'em up too hot in conjunction with the jet of pure oxygen from the torch could burn the chambers themselves. This is why you do NOT keep the burn going for any length of time without letting everything cool off again.

In the case of cleaning the precups, I would try this only in the last case of desperation when all else fails.

Of all the years I worked on engines I never saw one carboned up to the extent that it caused a miss but why couldn,t you get the right size drill bit and maybe you,d have to extend it out with a piece of rod to reach down in to ream out the hole, just a thought.

Not worth messing with.....just get another chamber....their not that pricey and the fiddle time has got to be worth something;)

Took things apart again , the precups look about the same on all cylinders so this leads me to think it is in the fuel pumps. swapped number 2 and 3 injectors and it helped some but not perfect . I will price new fuel pumps and a set of injector nozzles on monday unless someone has a set here.
call 716-753-0056

Before you buy pumps and nozzles, send me a PM....I have a good source for both.

The enemy of carbon is water ! If you soak pistons or in this case pre-cups in water, the water will soften the carbon easier to scrape off ! Or you could try soaking them in a container of Carb Cleaner or take them to a frendly radiator shop. Glen