Abstract: A pressure washer includes a prime mover, a pump, and a spray gun. The spray gun including a handle with a first grip portion, a barrel including a second grip portion, a flow-control valve movable between an open position and a closed position, and a user interface to control the flow-control valve. A presence sensor is coupled to the second grip portion to detect the presence of the user's second hand. A first wireless system is electrically coupled to the presence sensor. A second wireless system is electrically coupled to the prime mover. The first wireless system transmits a start signal to the second wireless system when the presence sensor detects the presence of the second hand of the user. The second wireless system, upon receiving the start signal causes the prime mover to start operation.