Is it possible for someone to show normal liver function test and still have hemochromatosis?

Unlikely: Often it is the workup of elevated liver enzymes ast & alt that discovers hemochromatosis. See http://www.Medicinenet.Com/iron_overload/page3.Htm.

Yes: A majority of hemochromatosis patients do have elevated transaminases especially later. If you have the high serum ferritin and/or symptoms and/or genetic studies sufficient to justify starting phlebotomy, don't hesitate.