Failures of shuttle fuel gauges - part of a critical safety system - forced back-to-back launch delays earlier this month.
NASA had been aiming for a Jan. 10 liftoff of Atlantis with a European lab for the space station. But shuttle program manager Wayne Hale indicated last week that the launch likely would be delayed after a test pointed to a bad connector.
On Thursday, Hale said it would probably take a few days or weeks to pinpoint and solve the problem. But he said it was too soon to announce a new target launch date because so much work still has to be done.
"At this point, schedule is not paramount in my mind," he said. "It's going to take as long as it takes ... days to perhaps a couple weeks. We have to get our hands around exactly what work needs to be done."
Last week's fuel tank test indicated open circuits in the connector that passes through the wall of the fuel tank, linking wiring between the gauges in the tank and Atlantis.
Senior NASA managers decided Thursday to remove a plug and electrical connector from the tank and send it to an Alabama testing facility to be studied and repaired, Hale said.
At this point, it appears all the work can be done while Atlantis is on the launch pad, he added.
The space agency has been struggling with sporadic fuel gauge problems for two years, ever since flights resumed following the 2003 Columbia tragedy. The gauges prevent the shuttle's main engines from running on an empty tank, which could be catastrophic.
NASA is facing a 2010 deadline for completing the space station and retiring the shuttles.