If the print head is not built into the carts, I would get/make up some cleaning solution (IPA, ProGly & distilled water), get some new empty carts, fill them up with the solution, then run many cleaning max cycles to flush out the printhead & ink pads.
If the printhead is removable, hold it under hot kitchen sink tap water, letting ti flush out all the intakes of the head until the water underneath is clear. (Just watch the splattering
)