How to replace printhead on Canon MX922 printers and post 2016 Pixma Printers

Make sure you are getting blank printouts when printing from the printers control panel, not just your computer. If it's printing blanks from both of these procedures, the focus would be on the "Printhead". Some Printheads are easy to remove, sits under the inks. Should be a grey latch you release to get access to the printhead. (remove inks first). Soak this printhead in a solution of windex, about a quarter inch deep, for about 20 minutes, wipe clean with isopropol alcohol and reinstall in your printer and do another alignment / cleaning procedure. If this does'nt fix the issue, you might try replacing the Printhead or retiring this printer.

Yes, that is a printhead fail. Printheads are almost as expensive as a new printer for the Pixma iP4000. You can find the printhead on eBay, runs $50-$80. Better to put that money towards a newer printer. You can also look for scrapped or damaged i860, iP4000, MP780, MP760, MP750 model printers and salvage the printhead from those.

You may need a newer cartridge
See if the printhead has any abnomal markings.
You can compare it with the color printhead.
If the printhead is good, see if the ink is flowing through the printhead.
Fill the ink cartridge to maximum
Squeeze the sides of the ink cartridge, ink should flow out.
If ink is flowing out, remove any excessive ink with a paper towel.
Install ink cartridges, do NOT do any cleaning cycle.
Since your black cartridge is full, cleaning may cause it not to print.
Do some black copy operations.

If you have generic inks you need to try another ink before replacing the printhead, if they are Canon inks, you need a new printhead.

your machine is getting on in age a bit now sounds as it needs a new print head, if you remove the printhead and physically give it a good clean and replace back in machine and do a head clean and your prints are still bad you need a new printhead
Canon Tech