Abstract: A self priming pump having a pump housing including a suction passage and a discharge passage. A pump chamber with an inlet and an outlet is also provided in the pump housing. A pump impeller is arranged in the pump chamber and has a suction opening opposed to the inlet of the pump chamber. A working fluid chamber is provided in the pump housing and is connected to the outlet of the pump chamber and to the discharge passage of the pump housing. A jet pump diffuser is provided directly upstream of the pump impeller. The jet pump diffuser has an inlet which is in communication with the suction passage of the pump housing and cooperates with the outlet of a jet pump drive nozzle within the suction passage. The inlet of the drive nozzle is connected to a supply passage which is connected to a supply passage which is connected to the working fluid chamber. A bypass line leads from the suction passage to the outlet of the diffuser while bypassing the inlet thereof.