Just went through this ourselves on our VP 540. It appears that you have a leak in one of the dampers - it will only get worse and if it hasn't already, it can take the black head down with it. They are pretty easy to change yourself - just be careful when removing the lines that you don't get ink everywhere. The cost of the dampers are about $60 each and there are 2 on each head. Better to change them both rather than just one. Much cheaper than the cost of a new head!
Edited to add: After you change them you have to pump ink through the lines - immediately after the change, we lost ALL the black head until we got the ink flowing again (multiple machine cleans - watch the drainage bottle!)
