Karcher K2 pressure washer (faulty) (Tanner St, SE1)

Dirty on the outside but had otherwise been in good working condition. Historically been temperamental running off an internal kitchen tap due to low pressure but functioned fine off an outdoor tap

Plugged in for the first time in a couple of years and wouldn't switch on. Googling suggests it's probably just an air blocked and low pressure but either way I'm needing to get rid of it. Strongly suspect just run water through to flush out air bubbles and plug into a proper outdoor tap and it'll work fine.