How can I set my Canon i560 to print only black?

SOURCE: Canon i560s prints all colors except black

If black cartridge doesnt work, the printer brins up black by comination of all 3 colours, but with no such good contrast, exactly as you describe.

The malfunction of black colour can have many reasons (like cartridge problem, printhead problem or electrical contacts problem in the printer, etc) so if you use Canon genuine cartridges ask a service to identify the problem, fact is that black dont work at all in your printer.

SOURCE: Printer doesn't pring

Try cleaning the printheads
Performing the printhead cleaning procedure

1. Power on your printer, press and hold the "RESUME" button until the printer light flashes once.Note: You can also clean the printhead by clicking the Cleaning button in the Maintenance tab of the printer properties dialog box in Windows; or clicking Cleaning pull-down menu in the Printer Utilities dialog box on a Macintosh computer. Choosing this option will allow you to select all nozzles, black or just the colour nozzles.
2. Pressing Resume on the printer will clean all nozzles. When the printhead cleaning begins, the POWER light starts flashing. This will continue for about 30 seconds. Wait for the light to stop flashing before you resume normal operation.3. Perform the Nozzle Check Pattern test again
3. If the results are satisfactory, resume normal printing
4. If the results are not satisfactory, you may need to execute a printhead deep cleaning.

SOURCE: Canon i560 won't print black text anymore

I had the same problem, even when I only selected grayscale printing, my printer would use all 3 colors to make black, and my black cartridge would never get used. Try this:
On printing preferences change your Media Type to Transparency.
This should solve the problem and stop robbing your color tanks when you just want black

SOURCE: canon i560 printer

It's likely the print head is clogged. You have 2 options:
1) Remove and clean the print head. Open the printer and lift the gray lever and just pull out the print head. There are no tabs to push, it simply slides out. Search the web for cleaning techniques. Looks like people have tried hot water, isopropyl alcohol, and ammonia. I don't know what the best technique is. It's probably a good idea to finish with a distilled water rinse and soak up the excess water with regular towels or paper towels. Remember to clean the ink jet at the bottom of the print head and not the electronic circuitry at the back of the print head.
2) Buy a replacement print head for $50-$65 off the web.
Hope that helps :-)

SOURCE: Canon i560 not printing, status light flashes 4 amber 1 green

4 blinks of the amber light says that the ink is empty, at least 1 cartridge is empty.