CAPE CANAVERAL - NASA fueled space shuttle Atlantis on Wednesday, but it was only a test leading up to the last flight of the 30-year program.

Space shuttle Atlantis sits on launch pad 39A after rolling out from the Vehicle Assembly Building at the Kennedy Space Center in Cape Canaveral, Florida June 1, 2011.[Photo/Agencies]

Liftoff isn't until July 8. Shuttle managers want to make sure that repairs to the external fuel tank are good and that no cracks pop up in any of the support brackets.

Preliminary checks indicated no cracking. But a valve for one of the three main engines recorded lower-than-normal temperatures during the tanking operation, indicating a possible hydrogen fuel leak. The engine was isolated, and the test continued.

NASA officials said even if the valve needs replaced, they believe they can make a July 8 launch.

The original cracking problem, meanwhile, kept shuttle Discovery grounded late last year. The same kind of patches - applied to the aluminum struts in the center portion of the tank - were used for Atlantis.

The struts, or brackets, are located in an area where there is no fuel, only instruments. The brackets were made from an aluminum alloy that was more brittle and that, combined with assembly issues, led to the cracking on Discovery's tank. Technicians will X-ray the brackets on Atlantis' tank beginning this weekend.

Wednesday's fueling operation was delayed several hours by thunderstorms that pounded Cape Canaveral on Tuesday. Three lightning strikes were reported near the pad. Preliminary checks show nothing was damaged, although a power circuit went offline.

A countdown rehearsal for the final flight will be conducted next week with the four Atlantis astronauts.

NASA is still analyzing a pair of issues from Endeavour's recently completed flight.

A glob of grease apparently caught fire around the left main landing gear when Endeavour landed June 1, but left no traces. The brief flash fire was caught on video, NASA spokesman Allard Beutel said Wednesday. Neither the crew nor shuttle was in any danger.

And the loss of foam insulation from Endeavour's tank during liftoff on May 16 appears to be age related, Beutel said. At 10 years, it was the oldest tank ever flown.

Atlantis will be packed with supplies for the International Space Station, so that the orbiting outpost is well stocked until a private cargo carrier arrives. NASA officials expect the first supply run by a US company could take place by year's end.

This will be the 135th and final mission of the shuttle program. NASA is under presidential direction to shift from orbital flights to expeditions beyond.