Isn’t there a flow switch? Mine has a Flow Switch as a safety feature that came with the cell. While I understand what you are trying to do, it is not safe for you or the equipment. If the cell has been on any significant amount of time with no flow, you have likely damaged it.
See this Article
That’s why I use a B&W Lazer printer, and have dedicated prosumer Canon photo printer for the few times I need color prints.