[dsy1]

The piston on the pump runs off a lobe/cam on the wiper motor. The electrical connection on the pump activates a solenoid to engage the pump when you push the wiper switch in. If you remove the pump you can see if the solenoid is working, but the pump piston won't move unless it is still mounted on the wiper motor.

If you have good access you can run a rubber hose to the inlet side from a jar of water, and see if the pump sucks up the water and pushes it out the outlet hoses. If you leave it attached you should be able to hear the pump cycling (a repeated clicking noise) if it activates. If not, check your switch or the wiring from the switch to the pump.