A fuel system has a jet pump assembly that fills a fuel reservoir for providing a reliable source of fuel to an electric motor fuel pump located in a fuel tank for a combustion engine. The electric fuel pump preferably delivers fuel at a controlled pressure to a series of fuel injectors of the engine. A small portion of the fuel exiting the electric fuel pump is diverted to the jet pump assembly that aspirates fuel from the fuel tank and into the reservoir. A biased normally closed pressure responsive valve prevents fuel flow to the jet pump when the electric fuel pump is running under impaired conditions, thus providing all the fuel to the combustion engine typically during cold engine start conditions.