Problems with starting a 2000 Ford Expedition usually relate to:
* The starter motor itself: This is the most common culprit.
* The battery: A low or dead battery is another frequent problem.
* The battery cables: Corrosion or loose connections can prevent sufficient current flow.
* The ignition switch: A malfunctioning ignition switch will prevent power from reaching the starter relay.
* The neutral safety switch: This switch prevents starting unless the transmission is in Park or Neutral.
* The starter relay itself: While not fused directly, a bad relay will prevent the starter from receiving power.
Instead of looking for a "starter relay fuse," check the battery voltage, the condition of the battery cables, and examine the starter relay itself for any visible damage or corrosion. You can test the relay using a multimeter or replace it as a troubleshooting step.