The fuel pump relay may be suspect if the car seems to lose power while driving or will crank upon key turn but not start. Replace this relay before it leaves you stranded .The fuel pump relay plays an integral role in getting fuel to your engine for combustion. Powered by the ignition and/or powertrain control module (PCM), the fuel pump relay's main function is to provide the fuel pump with enough power. When the fuel pump relay isn't working, then the fuel pump cannot either.