Specs Cars

1. Wiggle the steering wheel while turning the key. If there is pressure on the steering wheel that holds it on the lock pin, the key will not turn. A locked steering wheel is not the source of the problem if the steering wheel turns but the key still does not turn.
2. Start the car with a spare key. If the spare key works but the main key does not, you obviously have a bad main key. A replacement key for the E320 costs around $200 as of January 2011. You will need a valid registration and title to complete the purchase.
3. Place the key in the ignition and listen for a clicking noise. If both the spare key and the main key fail to turn, and you hear a clicking noise when you insert the key into the ignition, you most likely have a bad ignition switch. Visit a Mercedes-Benz dealership or a repair shop to confirm this diagnosis. A new ignition switch for the E320 will run you about $1,000 as of January 2011.

1. Locate the fuel pump relay, which is located under the hood on the passenger side near the firewall. The fuel relay will be either light green or blue in color. Remove the fuel pump relay from the connection and store safely. Crank the vehicle and idle until it runs out of fuel.
2. Disconnect the negative battery cable from the battery using a metric wrench.
3. Locate the fuel filter, which is located on the passenger side of the car, behind the rear tire and in front of the gas tank. The filter will be attached to the bottom of the car with a bracket held by a bolt.
4. Remove the fuel filter bracket by loosening the bracket bolt with a ratchet, extension and 12mm socket.
5. Place a fuel line clamp two inches from the fuel filter toward the gas tank.
6. Position the catch pan under the fuel filter to prevent a fuel spill. Use the screwdriver to remove fuel line clamps on each end of the fuel filter.
7. Using the pliers, remove the fuel filter from the fuel lines.
8. Position the new fuel filter with the flow marking pointed toward the front of the car and away from the gas tank. Slide each fuel line onto the new fuel filter.
9. Replace each fuel filter hose clamp and tighten, using the screwdriver. Remove the fuel line clamp.
10. Secure the fuel filter with the fuel filter bracket. Tighten the bracket bolt with the ratchet and socket.
11. Insert the fuel pump relay into the connection and connect the negative battery cable to the battery.