Alpine mrd 1001 problem!!?

hopefully sum1 can help me here, i have an alpine mrd 1001 watt amp conected to a 15" lightening audio sub, i am using 4 gauge power and ground wires, rca and remote wires connected properly. when my car is nt started the amp shows 9.0 volt and it pounds oryt but wen i start my car the volt just drops and the amp cuts of and neva s bk on. it states current on the amp. is their any way i can resolve this issue??