Please please please someone help I’m going mad.2005 gti Le rfi . When you press the start button it’s like you have a flat battery. It goes to turn over but just won’t. If I attach my little jump pack it cranks over flat out .I have changed the battery the solenoid the positive and negative battery leads but still the same thing. I tryed a bigger battery out my car but still sluggish and won’t turn over but as I said attach my little jump pack and it cranks over no worries. I don’t know what to try next