Thread in the slide hammer, after removing the glow plug, and hammer out. Not a big deal if the threads are ok. Thing is, even the slide hammer can damage the threads. The angled injector setup isn’t great for removal. The threads are weak.

I’d chase the threads on the prechamber. And be prepared to have to cut new ones and use some kind of adapter to hammer it out.

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (116k)
1991 350SD (206k)
1991 300D (228k)
2008 ML320 CDI (199k)
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Past Diesels:
1983 300D (228K), 1985 300D (233K), 1993 300D 2.5T (338k), 1993 300SD (291k)