The 7.3L diesel engines are equipped with a fuel/water separator in the fuel supply line. A "Water in Fuel'' indicator light is provided on the instrument panel to alert the driver. The light should glow when the ignition switch is in the START position to indicate proper light and water sensor function. If the light glows continuously while the engine is running, the water must be drained from the separator as soon as possible to prevent damage to the fuel injection system.
- Shut off the engine. Failure to shut the engine OFF before draining the separator will cause air to enter the system.
- Place a suitable container under the drain tube.
- Unscrew the drain valve to open it and allow the valve to remain open for 15 seconds or until clear, water-free fuel is flowing.
- Close the drain securely until liquid is no longer flowing.
- Start the engine and check the "Water in Fuel'' indicator light; it should not be lit. If it is lit and continues to remain on, there is a problem somewhere else in the fuel system.