To find it, you'll likely need to:
1. Consult a repair manual: A Haynes or Chilton manual specific to your 1994 Ford E-350 will provide diagrams and precise location information. This is the most reliable method.
2. Look for the washer fluid reservoir: Locate the washer fluid reservoir (usually a plastic tank). The pump is usually connected directly to it. Follow the fluid lines from the reservoir; they should lead to the pump.
3. Remove the passenger side splash shield (if necessary): You may need to remove some under-body panels or splash shields to access the pump.
4. Use a flashlight: Carefully inspect the area behind the bumper near the fluid reservoir and headlight, using a flashlight to get a good view.
Be aware that working under the vehicle requires proper jacking and safety precautions. If you're unsure, it's best to have a qualified mechanic locate and replace the pump.