Ford 1210 won't stay running

[tree grower]

A couple months ago I started a thread concerning my tractor starting but would not stay running --repeatedly. I put in new fuel, new fuel filter, bled all the lines, and finally declared victory. I started it today, worked it for about 1/2 hour, and the problem returned. It will start, not respond to throttle, then quit---repeatedly. I let it sit for a couple hours, started it right up, drove it into the shed. I have no faith that I could embark on a day's work with any confidence that it would stay running. It appears to be that it starts and runs fine when cold, but dies when up to operating temperature. Research of this page suggests that compression is probably adequate if it starts reliably--it does. After draining the fuel tank, removing and cleaning the drain valve/ sediment bowl assembly, installing a new filter and fuel lines, I can't see where there is any impediment to fuel flow to the pump. I also find it unlikely that the function of the injector nozzles is affected by normal operating temperature. I have not disassembled the injectors or overflow lines, and the injectors have never been cleaned or serviced. I welcome any recommendations of how to pursue this problem.