HP Deskjet 9800 Printing Problems

I have an HP Deskjet 9800 printer that has issues with printing. When
I print test pages, the color is either non-existent or streaky.
Yellow is the only color that consistently displays. I've tried
cleaning the print cartridges several times (using the software
utility, of course), and there's been no noticeable difference. At
first glance, this would appear to be just a shortage of ink, easily
solved by replacing the cartridges. However, I've done that, and the
new ink cartridges function exactly the same. Is there some other
possible cause for this that's not immediately obvious?