The oft-delayed second flight of the space shuttle Columbia may have to be put off for two weeks instead of one, which will force fresh delays on its third test flight next year.

Technicians at the Kennedy Space Center this afternoon were due to start the laborious process of removing the three auxiliary power units that drive Columbia's hydraulic lines, two of which have clogged oil filters that forced postponement of Wednesday's flight of astronauts Joe Henry Engle and Richard H. Truly. Depending on what engineers find when the power units are removed, the flight will be rescheduled for the middle of next week or the week after.

"If we have to replace the power units with fresh ones we're not talking next week, we're talking the following week," Shuttle Operations Director George F. Page said today at the Kennedy Space Center. "It all depends on how much contamination we find in the lubricating oil when we remove those units."

Postponed twice from its original launch date of Sept. 30, the second flight of Columbia was called off Wednesday morning when two filters feeding lubricating oil to the power units for the shuttle's hydraulics jammed in the final moments of the countdown. The hydraulic system swivels the engines in flight to steer the craft in space, feeds them fuel on takeoff and controls the elevons, rudder, speedbrakes, bodyflaps and landing gear at touchdown.

The mishap forces new delays in a four-flight shuttle test schedule that is already more than two years late. A two-week delay would move the third flight from January to March.

"Every day we're late now, we're that much later in our turnaround time downstream," Page said.

Technicians will remove all three power units so that engineers can inspect them, even though only two units showed signs of trouble on Wednesday. Page said it would take at least 32 hours of around-the-clock shift work to disconnect and remove the power units, complicated pieces of plumbing that weigh more than 100 pounds apiece and are located in a hard-to-reach aft portion of the spacecraft.

Sometime Saturday, Page said, the seven and a half quarts of lubricating oil that feed the three units will be drained and analyzed for contamination. The oil could be clogged with a wax that forms from contact with the hydrazine fuel that powers the unit. The oil and hydrazine are separated by seals that could have developed leaks just before liftoff.

At the very least, Page said, the lubricating oil and filters will be replaced and the pencil-thin lines that carry the oil to the filters will be flushed and purged with nitrogen gas. Should engineers find the contamination so serious that the units might have failed in flight, then all three power units will be replaced and the second flight of Columbia will slip two weeks instead of one.

"New units must be certified for flight and that means doing a hot run on them in the vehicle, which takes up a lot of time," Page explained.

He conceded that shuttle officials will reexamine their maintenance requirements between shuttle flights to see if they should change the oil filters and the oil for the power units. Page noted that the two power units with the clogged oil filters had been on the first flight last April while the one filter that didn't clog was new.

"We're not talking about one of those $25 oil changes you see in the paper," Page said. "But this is something we're going to seriously look at in the future."