If the pins behind the printhead are clean and not worn through (by repeated cartridge movements when printing) and the printhead pins are clean and sprung, then the ink or printhead itself just could be the cause. However if a new cartridge and a new printhead don't fix it then I think you're out of easy options. If, as has been suggested, the ink's blocked in the printhead it's surprising that not even a little gets through because it's always reported as an all-or-nothing problem. I'd think that the "thing" that selects the black cartridge has stopped working and that this "thing" is in the electronics in the heart of the machine. This problem killed my two ESP 5250s and it happened immediately, with no transition between OK and not OK.
Answers & Comments
If the pins behind the printhead are clean and not worn through (by repeated cartridge movements when printing) and the printhead pins are clean and sprung, then the ink or printhead itself just could be the cause. However if a new cartridge and a new printhead don't fix it then I think you're out of easy options. If, as has been suggested, the ink's blocked in the printhead it's surprising that not even a little gets through because it's always reported as an all-or-nothing problem.
I'd think that the "thing" that selects the black cartridge has stopped working and that this "thing" is in the electronics in the heart of the machine.
This problem killed my two ESP 5250s and it happened immediately, with no transition between OK and not OK.
Ink has either dried up or ran out. try running a head cleaning function a printing a test page