Dull colors on half the page

Put paper in the manual feed tray. Print. When the page gets half way into the printer, open the cover. Remove the toner. Look down at the paper. Is the right side lighter than the left? If yes, replace the toner cartridge. I don't believe that a fuser could cause your problem.

I have seen bad laser scanners cause this...
A black line across the page from left to right, of various widths, at various intervals, all the way down the page.
First, though, I would reseat the toner cartridge. If the problem disappears, you are in luck!
Try another Toner Cartridge to see if the problem disappears.
It could also be a bad control board.
Good Luck.

Hi,
I also had this problem with faded print down the left hand side. I decided to strip the printer down. I had to completely remove the laser imaging unit which meant removing all the covers and a couple of circuit boards. I then cleaned the lenses/mirrors inside the open front and laser head (behind a flap with laser warning sticker) with compressed air. This cured the problem but took a couple of hours. I wouldn't recommend doing this unless you are reasonable competent with electro mechanical devices.
Having seen the laser imaging unit out of the printer, it seems a real shame that it wasn't manufactured to be air/toner tight as this could have been achieved at a small cost.
I hope this is helpful ;)

You should contact Dell about returning these for a replacement, it sounds to me like a manufacturer's error.

Need to Clean the Lance located

the problem is not with the printer but it is with the ink that might be damaged, this is located inside the printer

One of the ink nossels are blocked you can use benzien or hot water to unblock them

Had a similar problem. Tried lost of things. In my case, the streaks cleared up after I cleaned the toner drum.

Check your Toner Carts.
Is the line a certain color?
Black perhaps?

Lift the door of the toner cart.
If you see a streak on your toner drum, you will see a streak on your paperwork.

Look at your fuser as well.
Is there a problem with the big orange roller?
BEWARE! Don't touch the fuser roller its EXTREMELY HOT!
Let the printer cool down before inspecting.

inside the toner unit, there is a stirring device to broadcast toner over full width of drum. I will guess this is the culprit, the stirring device is not turning. Try this test: remove the toner cartridge and shake it rapidly back and forth. Then try a print, any change?