Humidity plays a huge roll in the function of your printer, so if it's "very dry" in the winter months (like it is here), then I recommend you get a humidifier for the printing environment and maintain the humidity levels around 40-50%. At our studio, we run humidifiers during the dry winter months, and ACs' all summer to maintain proper humidity levels, to keep our printers in good working condition (along with regular use and proper maintenance).
Being nearly three years old, it could very well need new parts, such as dampers/ink selector, wiper blade, pump (with this printer, the pump comes as one unit with the capping station, flushing box and wiper blade). It's impossible for me to diagnose what's wrong with your printer, but I suspect the dampers and/or pump unit- replacing both parts would cost about $430 from www.compassmicro.com, which is a lot less than buying a whole new printer, but can add to $ already spent trying to fix this printer, and if not successful is a waste of $ (but if spending a few hundred fixes this printer, spending a few thousand on a new printer could also be considered wasteful).
The only way a printer knows how much ink is in a cartridge is by reading the cartridge chip. If ink isn't actually flowing from the cartridge, but you've done several cleaning cycles than make the ink level read much lower than it actually is, then you can try resetting the cartridge chips- but this will make the cartridges read full again, so you can risk running them empty and getting air in the ink lines.
I hope this helps, best regards~ Dana