Why doesn't the helium currently in the Sun's core undergo fusion?

Answer 1

There is still an abundant supply of hydrogen producing radiation pressure that prevents the sun's gravity form collapsing to form enough pressure and heat for the fusion of helium.

Answer 2

It does but there is alot of it. When all of the fuel is exhausted we grow very large, cool down, collapse and then explode. But this wont happen for quite a while

Answer 3

Perhaps it does and that is why the sun produces so much energy