Q: I bought an 2004 Audi A6 Quattro Sedan mode l3.0 v6 4 door for $1,000. The owner said he think it's the transmission and battery.

If gasoline was left in the fuel tank for more than 3-6 months, the tank would have to be thoroughly drained. Old gas will NOT start an engine. The fuel filter should be replaced as well. If the car has sat for a really long time (greater than 6 months), it may be necessary to remove the fuel injectors from the fuel rail and send them to a lab such as Mr. Injector for ultrasonic cleaning on a machine. During such service, the internal, very fine mesh filter baskets in the injectors are removed and replaced with new filters, and then injector output and spray pattern is measured and documented. Old fuel causes lots of problems and will plug up fuel injectors.

Once you have addressed the fuel issue, as needed, please note that "new" batteries are not always sold fully charged. Verify that you have a fully, 100% charged battery. Confirm that the engine immobilizer system (security system) is not activated thus preventing the car from starting. If the immobilizer system is on, you may see a security warning light. If the warning light is on, to temporarily override the immobilizer system, see these instructions. If there is no starter motor operation at all, that is if there is no starter operation with the key held in the "start" position, the procedure is to test for power and voltage drops to the starter motor/solenoid. If there is no power, or a large voltage drop is measured, then the electrical circuit supplying the motor has a fault. That circuit begins at the battery and includes grounds, wiring (some of which is very heavy cabling), fuses, relays, the ignition switch, neutral start switch, and terminations. Basically, with a fully charged battery, and with the key held in the "start" position, the starter is either getting power or it isn’t. With the key in the "start" position, if the starter motor is getting power but the starter doesn’t work, then the starter is condemned and replaced. Note that starters can and sometimes do develop intermittent faults due to bad spots on the armature. The bottom line is if there is battery voltage to the starter (and no excessive voltage drop) and yet the starter doesn’t work, it’s dead. Regardless of the underlying cause of the no start condition you are experiencing, if you request a no start diagnostic the responding certified mechanic will get the problem diagnosed and repaired for you promptly. Please let us know if you have further concerns or questions as we are always here to help you.