Digital BW, The Print

I have an Epson 1160 with CFS system from MIS running FS-N inks, until 
now without any troubles. I only print a few prints a week at this machine, 
but have always had a clean print without nozzles.

Suddenly I got problems with the black cartridge, like it was running out of 
ink ( not a single black dot came out!) Running several cleaning cycles 
helped nothing. When I took a closer look at the tube feeding the black ink, 
it looked like the black ink has dried out just before entering the cartridge...

I need an advice to get the ink flowing again... :)

Bjorn