There are several things to check related to fuel pump operation. It sounds like you have an intermittent problem so you need to determine if the voltage going to the fuel pump is consistent at the fuel pump relay. In the underhood fuse panel, right next to the fuel pump relay is a small blank, (empty) recessed terminal. It is connected, (inside the fuse panel) to the grey wire that runs to the fuel pump. When the ignition is initially turned to the RUN position, the terminal should show battery voltage for about 2 seconds and then drop to zero. It should show battery voltage continuously when the ignition is in the START position. Post your results.