Some fuel tanks may not have consistent welds between the fuel tank and the fuel filler neck, affecting the strength of the joint. In the event of a severe rear impact, an improper weld can result in a crack in the joint. This could illuminate the Check Engine Light, cause a fuel odor, or allow fuel to leak out. Any fuel leak increases the risk of a fire. Dealers will replace the affected fuel tanks to correct this concern. This recall is scheduled to begin on August 15, 2011. The Ford recall number is 11S20.