N2452C - Aircraft Aircraft Registration

The failure of the fuel selector valve in a position that restricted fuel flow to the engine, resulting in a total loss of engine power during initial climb due to fuel starvation. Also causal was the operator's failure to effectively detect and resolve the wear and progressive binding of the fuel selector valve before it failed due to excessive rotational force being applied. Contributing was the flight instructor's exceedance of the airplane's critical angle of attack during an emergency return to the airport, which resulted in an aerodynamic stall/spin.