Back to the ball in the chamber: If your injector spray patteren was not going where it is supposed to the fuel will burn there and can eventually start to burn through metal.
Some where there is a thread that tells you how to make a tool to pull the Pre-combustion chamber out (you attatch the slide wrench to it). Ebay is selling the correct tool but I have already been out bid on it.

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84 300D, 82 Volvo 244Gl Diesel