Your setup works for me if you change one setting in the "Thermal Liquid Properties (TL)"-Block: Pressure and temperature outside valid range to Warning. The problem seems to be the "Absolute Reference (TL)"-Block. It states:
"This block represents the absolute reference in a thermal liquid network where pressure and temperature are equal to zero."
Absolute zero is most likely not a valid range for your "Diesel fuel". But this is only in the starting state of the simulation. Maybe you can replace it with a "Reservoir (TL)"-Block. This is what I did, and it worked fine. Just remember to set a very big cross sectional area.
For testing afterwards I replaced your A1 Input Setup with a gas-reservoir, to simulate constant pressure. And as expected if I increased the pressure the flowrate also increased.
Regarding your Question with the Port: A2 is always an In- and Outlet-Port. You can test it by supplying very low pressure to the tank, and the Flow Rate Sensor will give negative values, meaning liquid is flowing in the other direction (towards the tank).
