The relays for the fuel system are located in the fuse box under the hood. There are two relays related to the fuel system: the fuel pump relay and the fuel injector relay. The fuel pump relay is responsible for turning on the fuel pump when the ignition is turned to the "ON" position. The fuel injector relay is responsible for turning on the fuel injectors when the engine is running.
Here are the steps on how to replace the fuel filter on a 2004 Hyundai Sonata:
1. Park the vehicle on a level surface and turn off the engine.
2. Engage the parking brake.
3. Locate the fuel filter under the vehicle, near the fuel tank.
4. Place a drip pan under the fuel filter to catch any spilled fuel.
5. Use a wrench to loosen the fuel line connections on both sides of the fuel filter.
6. Remove the old fuel filter.
7. Install the new fuel filter.
8. Tighten the fuel line connections.
9. Start the engine and check for leaks.
To replace the fuel pump relay and fuel injector relay, follow these steps:
1. Open the fuse box under the hood.
2. Locate the fuel pump relay and fuel injector relay.
3. Pull the old relay out of its socket.
4. Insert the new relay into the socket.
5. Close the fuse box.
6. Start the engine and check for proper operation.
