Wheeling right now and my gas was spilling out of my gas cap. When I opened it the gas shot out on me. Then it just boiled for awhile.In my head at least, there is enough fluid moving through the line that ambient temps shouldn't impact the temperature of the fuel line and any thermocouple in good contact with it. To support this, I noticed a metal guard on the driver's side frame rail over the blank fuel line and believe that surrounds the fuel filter installed in other markets. A filter would have a lot of surface area for the flow rate, and therefore allow radiant and convective heat to impact fuel temps. Toyota makes no attempts to similarly shield regular fuel lines unless they get into really close proximity to very hot things.
But, with a temp reading solution we could monitor temps of the line as it exits the pump module, goes along the frame rail, then enters the engine bay. And back.
Good points.