Hi every one i need some help im trying to put a new radio in my car, i hooked it up it works fine with the key on but when i start the car i have no sound it still has the factory amp. thanks splm

 

that would be a strange problem. I always recomend bypassing the amp as it is easy to do and nothing more then a noise maker. It is not hard to do if you want to do it, but I don't know why it works with the key on and engine off.......