Which of the following actions should be performed first in response to a WIF alert?

When responding to a Water-In-Fuel (WIF) alert, the correct first action is to drain the water separator sump. This is crucial because the primary purpose of the water separator is to remove any water that may have accumulated in the fuel system. Allowing water to remain in the system can lead to corrosion, fuel degradation, and potential engine damage.

Draining the water separator sump addresses the immediate concern of contamination, thereby preventing water from reaching the engine. After this step is completed, it would be appropriate to check the overall fuel quality and consider replacing filters or separators based on the extent of contamination found.

In this context, replacing the water separator or fuel filters should follow the initial draining process, as these actions would be more effective after confirming that the bulk of the water has been removed. Checking fuel quality serves as an important step but is more relevant after ensuring that the water has been eliminated, so it is not the immediate first action.