What you want is that when you open any key the pump turns on and generates pressure in the hydraulic system, and that it turns off when you close the key, right? You necessarily need a slide that detects the pressure drop in the system to start the pump, and that detects the pressure rise in the system to turn it off. That is, a hydropneumatic system, with a pressure switch. There are hydropneumatic systems without diaphragm, but not without pressure switch.