where is the fuel pump located

Car was running poor. I changed the fuel filter along with the main fuel line, car was driving fine for a few hundred miles and was stumbling at times. When I stopped to get fuel, I noticed there was no pressure when I removed the gas cap.. Now the car wont start at all. there's no pressure in the fuel line. I was thinking it could be the fuel pressure regulator even though there's nothing leaking from there. the car will start but shuts off right away

CONNECT A FUEL PRESSURE GUAGE TO THE FUEL RAIL OR FUEL LINE, ( PRESSURE SIDE ), CHECK FUEL PRESSURE, IF NOT IN SPECIFICATIONS, CHECK FOR PCM CONTROL @ THE FUEL PUMP RELAY, & CHECK FOR POWER AND GROUND AT THE FUEL PUMP.