I have this problem too. The printhead is probably worn out/plugged so badly that running the clean printhead function no longer does the job. There is a similar product called WF 26** something on youtube that shows how to take the printhead out of the machine and do a deep clean. Problem with the 4630 is that the wiring straps are glued to the board in front, so this doesn't work. (at least as far as I know) If anyone knows how to take the straps off without damaging the electronics underneath, please let me know.
there is an ebay seller that will recondition the printhead for you for around $85.00 so you wouldn't have to do that part yourself. Or you can buy a new one, but those people need the number on the head to get you the right product. But since I haven't figured out how to get it out without further damage, my printer sits lonely upon the shelf for the past year.
Sorry if this isn't really the help you were looking for, but it may give you a place to start. Let me know if you find someone to help/figure this out even better.