Dark black streak down the middle of the page

check the drum or the heater roller in the fusing unit

Most likely the cyan ink is burnt. If the ink sticks are left unused (printing more black than color, this will happen.

Print the test pages for PQ troubleshooting from the control panel and examine each print. Cyan will probably have very dark streaks down the page, magenta should look normal, and yellow also will have dark stripes. You need to replace this burnt ink, and the only way is to print. From within paint (or similar accessory in other OS) Create a full page of cyan, and print about 100 - 200 pages, or until the cyan starts to clear up. Yes it is a waste, but much cheaper than a print head, Do this for yellow as well.

Ink tends to overflow at the bottom guide rollers and the roller gets coverd in ink and causes the black line!The best will be to take it to a dealer and have it cleaned!Good Luck!

If this started after cartridge was replaced, then it is probably defective.

Take the cartridge out and take a look at the print head. Clean the print head.
Put the cartridge back in
Try and feed paper (not printing anything on it, if you can not get it to just feed paper, print a blank page) and see if it still has lines. If so, you are probably going to have to clean ink from inside the paper feed area. If not, try using it for a while and if it starts again, get a replacement cartridge. You might want to save some of the bad prints to show the clerk and try to get the new cartridge under warranty.

if your problem is printer setup page in go
and select to the b & w print and ink setting
are dark print set and give your print page
problem is also

You'll have to open up the printer and clean everything off. You probably have a feed roller with ink on it. If you refill, use ONLY inks made for your brand of printer.

Hello sir;The streak line from printing also should be from copy, because the line come from imaging unit, check the meter count if close to or over 50,000 then replace drum and drum blade, it will take care the problem.
The brother printer you need to replace imaging unit( drum unit).

when you start using refill kits they messup you machine you will need to use the oem toner for the canon good luck canon sr tech

Dark streaks are an indication of "burned" or overheated ink. This will occur when the printer sets for a long period of time and nothing is printed. The problem will usually disappear after 50 pages or so, unless the printhead is damaged.

If the print remains dark, the printhead will need replaced.
(Very expensive)

(Dark print can also be caused by using Non-Xerox ink)

if you need any parts for that machine a have 4of them

Thank You,

Mikey