Caution: Before starting any work on your vehicle, make sure the engine is cool and the parking brake is engaged.
1. Locate the fuel filter. The fuel filter on a 2004 Duramax diesel is located on the driver's side of the engine, just below the fuel injector pump. It is a black cylindrical-shaped object with two fuel lines connected to it.
2. Disconnect fuel lines.
- Using a 17 mm wrench, loosen and remove the fuel inlet line from the filter.
- Using a pair of pliers, squeeze the release tabs on the fuel outlet line and pull the line off of the filter.
- _NOTE_:_ There will be a small amount of fuel that leaks out when you disconnect the lines.
3. Remove the fuel filter.
- Use a 24 mm wrench to loosen and remove the filter mounting bracket bolt.
- Once the bolt is removed, you can pull the fuel filter straight out of the bracket.
4. Inspect the old filter.
- Before installing the new filter, inspect the old filter for damage or debris. If the filter is damaged or dirty, it will need to be replaced.
5. Install the new filter.
- Insert the new fuel filter into the bracket and tighten the mounting bolt.
- Reattach the fuel lines to the filter.
- _NOTE_:_ It is important to make sure that the fuel lines are connected properly. If the lines are not connected properly, it could cause the engine to run poorly or even stop running.
6. Start the engine and check for leaks.
- Once the fuel filter is installed, start the engine and check for leaks. If there are any leaks, tighten the fuel lines until the leaks stop.
