To find the exact capacity for *your* van, check:
* The owner's manual: This is the most reliable source.
* The fuel filler door: The sticker on the inside of the fuel filler door sometimes lists the capacity.
* The vehicle's identification plate (VIN plate): While it might not directly state the tank size, this information could help you narrow it down if you contact a Ford parts dealer or use a vehicle identification number decoder.
Without more specific information about your van's trim level and options, a precise answer is impossible.