hp 2000c won't print black

[bronc]

hello
I bought a new hp 4844a cartridge £29.99! when i ran out of black ink. It now goes thru the motions of printing a pure black filled rectangle on my page but - nothing. (I left the cover open with no black cartridge when i went to buy the new cartridge.)
I've tried "priming" the cartridges and aligning them.
Are the cartriges ever to blame? Any ideas.

 

[PWP10]

If I remember correctly there are white ovals under each ink cartridge. They are spring loaded and the spring holder has a tendency to break. You can compare the spring action for each cartridge to see if that is the problem. If so you will need to repair or replace the ink supply assembly.

 

[bronc]

well thanks PWP10
I got a chap to look at it and cleaned the contacts for the black head and voila. Yes I know about those little springs. To refit them I recall the need for some very very long nose pliers which i just happened to buy in brick lane market a few days before (£1)for some very unknown reason. Thanks for your suggestion.
Ed