MP780 prints will not print black in photos, black text works fine

Not normally but the black print head nozzles maybe blocked.
Inkjet printers need to be used frequently to prevent ink drying out and blocking the print head nozzles.
If the print head cleaning maintenance routine does not clear the blockages, then print head needs replacing, but it may be expensive.
It may be more cost effective to buy a later model and better printer than replace the print head.

Run head cleaning and deep head cleaning for few times. If it doesnt help, you can try to remove print head, and clean the nozzles with distiled water.
And after that also run few times head cleaning mode.

Go to your printer properties box and do a nozzle check then head cleaning and that should resolve your issue..

Perhaps the CMY color heads need alignment. If you have not already done so, run a head alignment from the driver maintenance section. It will print out a page containing several lines and text, and request you select the closest-aligned images. After this is done, do another image print to check for improvements.
Normally, the printer uses the black cartridge for text and the CMY inks for images (even for black on photo and specialty paper). So when you are printing normal text pages on plain paper, only the black ink is used. A good check for this would be to print a normal text page, but select photo paper in the driver to trick the printer into using the CMY inks to make a substitute black text page. If this looks ok, then you are having issues other than cartridge alignment.

Hi. the problem is the print head, maybe is clogged or damage, try this remove the cartridges , and the print head and submerge the print head in hot water for 3 minutes, dry the print head and reinstall it, if problem persist replace the print head.

TCT How to remove and clean Canon Printhead

Same problem. Will print web pages in color, diagnostics work, but will only print photos in black.

Head Align Failed

All the people in this forum with a Canon ink printer not printing black, especially if you tried replacing the print head and still have the same problem.

Your purge unit/capping assembly is most likely clogged. This can be caused by using crappy ink cartridges and by not using the printer for exptemely long periods of time.

You will have to disassemble the printer. First open the lid so the print head moves into the centre of travel. Unplug the power cord. Remove the upper case (can be hard to do, usually they're snap-together).

Remove one screw on either side of the print engine and remove the engine from the lower case. Unplug the cables that go from the main board to the purge unit (the large black assembly covered with old ink, located on the right side of the printer where the head usually would stop after you've finished using the printer and shut it off).

Now you have to remove that black purge unit from the right side of the engine. Usually there are two screws holding it in place.

Give the unit a bath, carefully removing old ink from everything so the unit looks like new. (be sure to remove the one motor first or you will ruin the motor). Check the bottom and make sure the two small clear rubber tubes are not clogged with old ink. Clean the absorber off (the pad in the lower case) if it has ink piled into a small hill shape.

If the tubes look like they might be clogged, you'll have to find a way to clear them out. I can do it in my shop, but it's too in depth to explain.

Reassemble the printer, connect to a PC and do a few deep cleans and print out a test page. Problem solved.

Remember, if one colour is not working it's because the head is clogged. You will have to do multiple cleans to get it to work. If it still doesn't work, then either it's REALLY clogged or the purge unit is not working because it's clogged. If you buy a new print head, then the only thing left is the purge unit. Be brave and try the disassembly and cleaning, or take it to your local service shop.

We charge $45 CDN for a job like this.

Rule of thumb: If you can get it fixed at a shop for 1/2 prince of a new unit, go for it.

go here

http://www.usa.canon.com/consumer/controller?act=ModelInfoAct&tabact=SupportDetailTabAct&fcategoryid=238&modelid=10444

type in :
no black text.

Follow steps to fix your problem

Try to change the default printer and check ...

Also try printing from other documents see if you facing the same problem

What version of Works you using ?
Do you have the Dic for Works ?