Does your engine have Vapor Separator Tank ( VST) and if yes when was the last time you changed the filter screen inside the tank? Some of the dirt you referred to in the fuel /water separator filter could very well have clogged the VST filter. I included a link to a video that shows typical servicing of a VST. I have had the same problem you are experiencing with my F200. Engine would run fine then begin to lose RPM and backfire once in a while but would die shortly thereafter. Shut the engine off and it would start and run but then die. Then finally not start at all. Some but not enough fuel was getting past the VST to allow it to run normal. Also I learned the hard way that you should use a 10 micron fuel/water separator which helps prevent clogging in the future.
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