I picked up a second 4900 on e-bay mostly for parts, but it appears to be fairly functional and when I do a nozzle check all but a couple of channels print. a few of them have some missing nozzles, but they may just need cleaned. So I loaded up my piezo-flush cartridges and tried to do a ink charge to run the fluid through the lines and head using the SP. It completed the operation but no ink or fluid was actually run through the lines. The maintenance box had nothing in it. I tried a second time with the same results. So I am assuming that I have a bad pump or something. I am not really familiar with how the ink charge works. I believe that the ink is actually sucked up through the head, but I really don't know. Can someone enlighten me on what the problem might be and where to start looking? Thanks!!