damn amp wont work! aghhh help me!

ok i got dont hookin up my friends shit last night in his 99 gmc p'up. i put in a jvc cd player, a kole q2-980(ithink)amp and 2 12" power acoustics. well i wired everything right but when i go to plug the rca's in , it immediately goes on protect. the only reason i can think of is because i used a 4g power and an 8g ground, can this be the cause? if it is can i use some of the remaining power wire as my ground?