i have a 2006 f 150 4.2 liter yesterday it just quit in costco parking lot it turns over and fires a little bit but it won't run the tow truck guy said maybe fuel filter now i changed the filter but before i did i turned the engine over see if the pump was working and nothing happened so i seen the emergency shut off i pushed the button in still nothing now one question that shut off switch just went in and out didn't click or set is that the way it works? i checked fuses ok ground cables ok so what will cause the fuel pump not to work? or where should i look next?

thanks for the help !!!!