Ford's good 'ol "Powersmoke diesel". The engine that Ford sued International over. International (Navistar) got a real black eye over that one.
Yes, the plug has a tendency to blow out, among other things. You haul it into a Fraud dealer, and their "diesel specialists" will happily tell you that you need a new pump,($$$) and won't even look for the plug.
Ever wonder why they have so much trouble with the hydraulic control circuits on a "Powersmoke"? The main reason is; the pump is fed unfiltered oil from the sump. If you let your oil get dirty or overstay it's welcome, problems soon follow. The only guy I know that has never had a problem with his "Powersmoke" runs an auto parts store locally, and just happens to be the local Amsoil synthetic oil distributor. He has used Amsoil since his truck was new. Expensive, but he hasn't had any problems with it...yet.
No good deed goes unpunished.