Originally Posted by upallnight

Once the BST has blown, you will not be able to start the engine. The biggest draw on the electrical system is a starter. The starter circuit is feed from the BST cable. The airbag would have received the energize signal from the DME at the same time the BST cable would have received it signal. Some circuits such as the door lock and unlock circuit are not on the BST circuit so that they can still operate once the BST cable is blown. The fact that you can only start the engine thru a jump from the engine compartment jump terminal lead me to believe that you are back feeding the circuit from the battery jump cable.