To find the exact amperage, you would need to:
* Consult the vehicle's wiring diagram: This diagram will show the fuse or relay protecting the fuel pump circuit, which may provide a clue as to its approximate amperage draw. However, this is an *indirect* way of estimating.
* Use a multimeter: This is the only truly accurate way to measure the current. You would need to connect the multimeter in series with the fuel pump circuit while the pump is running to measure the amperage directly. Caution: Working with car electrical systems requires understanding basic safety procedures, or the help of someone who does.
Without either of those sources, I cannot provide you with a definitive answer.