Lets make sure first if it is the heads.
Get a syringe and attach a small 3 inch or so length to it with the tube the pump uses. While printer is off, move the heads off the capping station. Remove the pump tube from the capping station. Attach the syringe tube to that captop and set the heads back in place. Try to draw ink into the syringe.
Do you get ink and if so is it a nice mix of dark brown to a black color?
If no ink are you getting resistance in the syringe or do you hear air leaking?
If you hear air, is that small little rectangle box that has the clear tubes going to it over on the right side, sitting flush against a flat piece with springs pushing it against that box?
When you put the pump in did you run the extra length of line direct to the drain bottle or do they go to another line before the drain bottle. If so is that line clear and unblocked.
Start there and see what you find.