An A320 filled with the dirty socks smell after engine start resulting in burning eyes; a metallic taste; and headaches so the crew shutdown the engines; donned oxygen masks and were towed to the gate. The APU was MEL'ed for the same reason.

Narrative

Fumes at gate; dirty sock smell reported by B Flight Attendant. APU was on MEL due to Fumes; dirty sock smell. B Flight Attendant called flight deck after second engine start while still at gate to report dirty sock smell; at first we thought it might be air cart. Soon after Flight Attendant called we had a strong dirty sock smell on flight deck. I put oxygen mask on and called for jetway to be hooked up with external power. Captain immediately shut down both engines and we opened both flight deck windows. Flight attendant opened aft cabin door. When no one showed to operate jetway after numerous calls; Captain threatened to evacuate aircraft because we could not get any one to hook up jetway to aircraft. Response from Operations was go right ahead. Captain had burning eyes and metallic taste. Two flight attendants had headaches and I had a headache and metallic taste. After conversation with chief pilots office and fight attendant supervisors; approximately two hours had gone by and our symptoms went away. Crew decided we could continue our pairing; APU on MEL for same reason.