Well, for one thing, you're drawing the tetrahedron in line mode.  GL_CULL_FACE does nothing for GL_LINE. 

You might also try culling the front faces glCullFace(GL_FRONT).  If the results are expected, then reverse the winding order of the polygons (i.e., polygon [v1,v2,v3] specify as [v1,v3,v2]) and cull the back as before.

Ian