500k micro farad cap?

I bought subs and amp from my girls brother and they gave me a cap with it. I have not hooked it up. My subs always quit for a second when i use my turn signal and brakes at the same time. To much power pulling from the battery obviously. My question is will a farad help with this problem? And do no give me a useless answer like just throw it out they are useless. I didnt ask are caps useful. Thank you. PS my amp is 760 watts and my subs are 800 and 600.