2000 Expedition won't start

Dash lights up ok but will not crank. Found the starter relay located under the hood next to the battery and attached to the firewall. It received 12 Volts on the small screw input but wouldn't crank. Easy to replace, Got it from Autozone for $9.99. Funny enough it had given me no warning, it just quit all of a sudden and left me stranded. The car can actually be started by using a screwdriver to bridge the appropriate terminals.