However, it's not always in the exact same spot across all 4.9L engines of that year. Some variations might exist depending on specific engine configuration and the manufacturing date.
To be certain, you'll need to:
1. Consult a repair manual: A Haynes or Chilton repair manual specific to your 1991 Ford E-250 with the 4.9L engine will provide a diagram showing the exact location. This is the most reliable method.
2. Visually inspect: Carefully look around the thermostat housing and the cylinder head. Look for a small sensor with wires leading to the engine harness. Trace the wires to confirm it goes to the instrument cluster.
3. Use a wiring diagram: If you have access to a wiring diagram for your specific vehicle, you can trace the temperature sensor wire back to its origin on the engine.
Remember to let the engine cool completely before attempting to locate or work on the temperature sending unit.
