Karcher K3.99 pressure washer.Connections are sound, inlet water pressure high, nozzle set to high pressure. When I switch the power on, the pump starts running (I thought it was not supposed to run until I pressed the nozzle trigger) but it doesn't run continuously. It switches on and off rythmically. When I press the trigger on the spray nozzle it runs continuously and smoothly but the pressure is too low so it doesn't work as intended. Does anyone know what the problem could be?