HP Officejet 7310xi - black cartridge print quality

[wpctechsupport]

We have a "new to us" printer at church.  The person that brought it to us said it had some print quality problems with the black cartridge.  We installed a new cartridge because the old one was almost empty and the printer worked fine.  We set it up to be directly connected to laptops via a usb cable and have had success with both win XP and win vista. 

We are now getting some parts of the text being very light and almost nonexistent.  These areas are always in a line across the page.  The cartridge has hardly been used, but the printer has been mostly idle for the past month.  When I removed the cartridge today to take a quick look I noticed after a slight shake that some parts of the printer head were not producing ink.

I had a Deskjet 500 in the past that had to have a capping station replacement due to ink buildup that was clogging the nozzles on new cartridges.  I was wondering if the capping station on this Officejet 7310 is not seating properly and allowing the ink to dry in the print head?  I believe we can print if we run a purging cycle or replace the ink cartridge, but that will cost a lot in ink.

Is there a way to access the capping station to either clean it or inspect it?  I have checked the HP website and was not able to find information on this particular printer having this problem.  In my full time job, I have had some limited experience developing some components for HP inkjet printers, so I am relatively familiar with some of the components of these printers. I am willing to dismantle the printer if needed to gain access to the capping station.

Any help would be appreciated.  Thank you