Fuel tank is leaking fuel from the top, but no smoke leaks from the tank or pipes if you feed smoke through it.
Could be a leaking pressurized line squirting the top of the tank. In other words anything past the fuel pump near the tank. If a fuel pressure gage drops pressure fairly quickly after you turn the key off, can help confirm this.
Is the plate at the top of the tank that has the fuel lines on it really rusty? Replace it. I’d guess the leak is somewhere on that plate.