I found this which might be relevant :
Your printer may be printing fuzzy, blurry, or other faint text because of dirty print heads. All modern printers have some printer cleaning, self-test, or diagnose mode that can be performed to check and clean the printers print heads and other internal equipment used to print. It is recommended if you use your printer heavily or have had it for more than one year that you perform this function. This can be done either through the software included with your printer or by pressing one or more of the buttons at the same time on your printer. Additional information about how to do this can be found in your printers documentation.
Time : The Most Precious Commodity