Carves, what are the diesel engines like that come in the XJ's?
I'm not carves, but I play him on TV. Diesels in XJs:
North America, 1985-1988: Renault 2.1TD. Good engine, but the XJ was entirely the wrong application for it. The only other vehicle in this part of the world to use that engine in any significant numbers was the Winnebago LeSharo / Itasca Phasar motorhome. Yes, you can still get parts for it, but they're priced accordingly. Was used for a few years in
some European countries. May have been an option slightly longer in Canada.
Europe and the rest of the world, 1995-ish to 2001: VM Motori 2.5TD. Not a bad engine, but prone to head gasket failure due to too-small radiator and people not letting the turbo spin down before switching off. First XJ I ever drove had this and a 5-speed in it; was a good combination. Never offered in North America.
I know there was a diesel option for a few years in Canadian Jeeps, but they were apparently not that great in terms of power or reliability...
The problem wasn't so much that that specific engine was unreliable as that it just wasn't suited to the XJ; I can remember that same engine powering legions of Renault Extra and Trafic vans in Europe, and they were considered to be fairly durable in those vehicles. FWIW, no diesel engine in that class was particularly powerful at the time - the technology just wasn't there to extract the power levels they make today, but in its time it was considered to be one of the better small diesels.
In any event, toss Renault bailing from the US market in 1988 into the mix, and it's not surprising that very few have survived. They do periodically pop up on eBay, but, quite honestly, unless it's super clean and you want it as a timewarp example of the fact that they really did once make a diesel XJ for the US market, I'd pass. MJs got them as well; a couple of people here have them.