Got the C5180 from a relative because it didn't work. I tried a new
black ink tank, it doesn't print anything in black. Color print looks
weak and washed out without black for shadow, and black only print
comes out almost blank, just a few tiny black dots like I have an
empty ink tank installed.

I figured something is interrupting the flow of ink from the tank to
the printer head as the tank are mounted stationary on the front. Is
there any instruction I can use to take apart the 5180 (or any 5100
series) so I can check the connections?