My Pixma MG5250 has run out of Cyan ink, how can i continue to print with just black ink?

As long as the cartridge that is telling the printer I'm empty is in the printer, you can't go on. I did reset all my colour cartridges in my printer, because I only print in black. Still now and then a cartridge is telling it is empty. I think the printer still wants to mix colours in the black. Lucky me, I can reset my cartridges all the time.
I'm not sure you can do the same on the canon. Try to get a chip resetter that is sold on all refill stores.

Worn print head. And for what they charge for a stinking print head you can get a new printer for less with a warranty to boot!

The reason that there are two black carts is that one is for printing on standard paper, and the small one is for printing on photo paper. It's not a spare, and it is not supposed to use the small one when the large one runs out. You will need to replace the empty cart.

maybe the cartridge is wrong, release it and clean the electrical contacts, put them again one by one, if notting happen, try this
Solution As the printer operates, it moves ink from the ink cartridges into a printhead reservoir. The printer does not deliver a message when an ink cartridge goes empty, because it still has ink in the reservoir. The printer continues printing until the ink level in the reservoir falls to a first trigger point - then a message appears advising the printer owner to Replace Cartridges Soon . At this point, other cartridges that are empty but have not reached the trigger point are also mentioned in the message, to save trips to the retailer. After the first trigger point, the printer can continue printing until ink levels in the reservoir reach a second trigger point. At the second trigger point there is only enough ink left to perform vital servicing tasks, and a new message appears, saying Ink Cartridges Empty . The options offered depend on the usable inks remaining. If no options are offered, the cartridges indicated must be replaced before printing can continue. The Ink Cartridges Empty options are described in the table below: Ink colors out Option Print mode possible All Cancel None Black

AND

Cyan, Magenta, or Yellow (any or all) Black only Continue with other colors Cyan/Magenta/Yellow mode (composite black)

Text and photo quality will differ from those printed when all colors are available Light Cyan or Light Magenta (either or both) Cyan, Magenta, or Yellow (any or all)

(Black still available) Print with black ink only Grayscale

The ink cartridges on your Canon Pixma MP500
print head not problem your yellow cartridge &black
problem

enough ink b ut not printing at all - blank paper on every time despite noise as if printing

I think the problm lies between the ink tank and the printhead. When this passage runs dry, sometimes it takes time for the ink to fill this passage again. Try printing again after a day or two.

Sorry to say this, I had a Canon Pixma and it wouldn't print unless you replaced empty cartridge, although I did have some success for a while longer by pressing OK button?

Dear kalium,
First, check ink level information in printer status monitor windows. Does message ink low appear in status monitor?. It could be the cyan ink has run out. Please replace the cartridge with new one

1. Clean The Print Head Nozzles (Mac OS X) MP500 / MP800 2. Clean The Print Head Nozzles (Windows) MP500 / MP800 3. Confirm that the recommended ink tanks are installed properly MP500 / MP800 4. Install recommended ink tanks in the correct order MP500 / MP530 / MP800 / MP800R / MP830 5. Perform A Manual Print Head Alignment (Mac OS X) MP500 / MP800 / MP950 6. Perform A Manual Print Head Alignment (Windows) MP500 / MP800 / MP950 7. Perform the print head cleaning procedure on MP500 / MP800 8. Print Head Alignment MP500 / MP800 / MP950 9. Remove tape from the MP500 / MP800 ink tank 10. Replace ink tank(s) MP500 / MP800

I hope it helps!!!