Thank you, will check it out! The nature of the Canon engineering software design for this printer prevents me from making ANY print if the printer decides it is clogged. Unlike my Epsons, it "knows what's best" in the most frustrating manner.
Jeff, you've just entered the expensive wasteland of trying to resuscitate an unproven (prints normally, no error messages, clear nozzle check) high end used printer - in your case one that seems to have been treated badly in the past, in addition to being a "very low usage printer" - one of the worst things that can happen to these workhorses.
There's a good reason in Canon LFP's for not allowing printing with a defective head: the heads are electro-thermally activated with a huge redundancy of spare nozzles, and as nozzles eventually suffer burnout, spares are auto re-mapped transparently. As the number of shorted-out nozzles increases, more current is drawn through the controller board, which will eventually destroy the board if printing is allowed to continue. The same thing if supply lines are air-locked, without the cooling effect of the ink. You will undoubtedly have to replace both heads sooner or later at about $800 total, plus several hundred for the ink refilling the purged lines and new heads, and a new maintenance tank.
As seductive as a used high end printer may be, they are rarely bargains unless fully proven to function normally, as there's usually a good, expensive reason they aren't still in use. If you're not prepared to deal with a "project" printer with unknown deeper problems, I'd cut my losses by selling the remaining ink and roll spindle and disposing of the carcass.
Sorry to play the pessimist, but in six years of following the Canon LFP WIKI and this forum which has been an Epson resource, I feel this is a realistic take.
PB