NASA began another countdown Thursday for space shuttle Discovery after fixing electrical problems in an engine that delayed the shuttle's "Star Wars" mission earlier this week.

The countdown toward a Sunday morning launch started at 8:45 a.m. EDT.NASA's first attempt to send Discovery on its military mission was halted early Tuesday, less than six hours before liftoff, when an engine sensor malfunctioned.

Workers entered Discovery's engine compartment Wednesday to remove the sensor and an attached bundle of electrical cables. The sensor measures pressure for an oxydizer turbopump on one of the shuttle's three main engines.

NASA sent the sensor to Marshall Space Flight Center in Huntsville, Ala., and engineers were able to reproduce the failure.