If you mean you just cannot break it loose (i.e you have the right size socket and you've managed to wegde it inthere between the pully and the firewall) then I just slid a long (4') breaker bar over the end of the socket wrench and that gave me enough leverage.

If you don't have a long breaker bar, but you have a floor jack, sometimes they have hollow handles and are removable and you can use the floor jack handle as a breaker bar. Good Luck