My Canon i550 printer gives good results when it works but I find that if I don't clean the print heads and/or do a print head alignment check almost every other job, it doesn't print black text.
On the i550, and other printers in that range the cleaning mechanism was not as good as it could be and often results in the need to steam it. This problem is fixed in the new PIXMA IP range.
JeDi58
September 2004
It may be that the Black print cartridge is either faulty or running low. Are you using a remanufactured cartridge?