Car stalls then won't restart
So my Volvo stalled when I was at a stop light, and would not restart. It turned out to be the fuel pump relay because after jiggling the relays I was able to get it home. Since then I have gone to AutoZone and replaced the old relay with the most expensive one they had. Fast forward to today. I had been driving for about 30 minutes various places, and I turned on some music. I do have a subwoofer in the back and it's hooked up directly to the battery. The music was quiet, and the bass was turned down. I notice a sudden drop in power about a minute into the song (the sub wasn't doing much), and the engine comes back. I pull up to a stop light and after 30 seconds of being stopped, the car just stalls. I could not get it started again and we had to push it into a parking lot. The car still turns over really strong and I can hear the fuel pump coming on when I crank it. Could the sound system have caused the stall? Would that keep it from turning back on? Any help appreciated, thank you
