Printer using a black cartridge in one week. Loosing ink somewher

replacing a cartridge, while the nozzles are blocked won't help.
Realise the printer will mix there colours to get "black" on the paper. So even a full cartridge, can't make the other colours black till the blockage is gone.

Please try this. If you have ink cleaning fluid, (only for printer ink) use that, if you dont have cleaning fluid, use clean water.
Open the printer as if you replace a cartridge. Remove the black one and look tot the bottom of the cartridge holder. There is a little pipe, where the ink should go in. put some drops water or cleaning fluid in there leave it a few minutes. with a tissue dry it and again insert some drops of water or cleaning fluid. Then put in a cartridge and give the printer a black and white print job. Like print a few A4 papers. Let it print till the black comes back. Can take up to 4 pages A4. I hope this will unblock the nozzles.
Please even if you don't need to print, switch the printer on at least once a week. And even better, let it do a bit of printing every week. This will save a lot of frustration.

Greyscale is color not black only.
You can print in black and it will look grayscale only darker, printers are a pain to work with after a year has gone by, I can expect almost a half hour to print something with my $400 epson because one of the colors is out even though I never printed in the last year a colored page. I take the color cartirges out and they are empty, but I only print a page 2-3 times a year. I use the scanner all the time. Brother and epson have their print heads in the printer not the cartridge so make sure your inks are always have something in it or it will be miricle for the printer to last more than a year. Check colors every other week. One Epson printer only lasted 3 months because I never used it(print head dried up). Never use the set up with tubes running outside printer to small tanks of ink if you only use it occationally.

INK PROBLEM
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.

there is a utility in your printer software , using that you can clean the head of the printer, if this does not solve your problem use the alignment option from that utility

May have dried up...was it in a warm place...ink evaporates.

Canon PIXMA MX850 Multi Function Printer Printer Canon MX850 will not print from... Answer Canon MX850 will not print from small Black Ink Cartridge - 8BK. It only uses the large black ink... (More) Canon MX850 will not print from small Black Ink Cartridge - 8BK. It only uses the large black ink cartridge and I have a drawer full of small 8BK cartridges. How can I get it to use the small black cartridge and not the large black cartridge? Thanks

please change your printer cartridge
05 black
06 Color cartridge
it is problem code not cartridge part no
Thanks

Try reinstalling the printer, as it sounds like a driver problem. This shouldn't happen, but occasionally the drivers get corrupted. And refilled cartridges certainly don't help, and may continue to give trouble even when replaced with OEM ones. Have you tried turning the printer completely off - disconnecting the power lead, for a few minutes? That sometimes clears things.

Apparently, if you hold the "resume button" (the one next to the power button) for about five seconds after you get the message saying to replace the color ink cartridge the machine starts printing. I did this after I went to "maintenance" under "preferences" and changed ink to "black only." At first that alone did not work, but after trying the resume button for 5 secs it worked okay.

Sorry, no good news: Infact you need a new printhead. The refill ink has clogged the filter inside the head which is in front of the nozzles. Another reason could be: Did you unplug the printer from power in those weeks of none use? If yes, the head has dryed out. In future: Do one simple test print once a week when you dont use the printer too often. That keeps the nozzles going :) There is some hope, too: See here how to fix it on your own http://www.fixya.com/support/t209702-get_color_print_black_works_fine (Following the link given to hstt.net : choose mfc 215c inside)