The agency that buys autos for the federal government says it wants them equipped with the stronger bumpers that were rejected last July by another federal agency that sets automotive safety standards.

Gerald P. Carmen, administrator of the General Services Administration, said it would be an "agency objective" to have bumpers on the federal government's fleet of new cars that can protect them from collisions up to that 5 miles per hour. The government buys between 18,000 and 25,000 new cars annually.

The National Highway Traffic Safety Administration ruled in July that bumpers need only pass a 2 1/2-mph crash test, a change sought by car makers because of the lower cost of the lighter bumpers.

Carmen's initiative is being "intensively studied" by GSA's Office of Federal Supply and Services to make sure that the federal taxpayer saves money on repairs if the government buys stronger bumpers--which generally cost more--according to GSA Assistant Administrator Les L. Mitchell. "Right now, we are poring over data . . . to go beyond the question of safety," Mitchell said. "Because there are no real safety questions at that speed, the biggest question is cost."

Carmen, who operated a state-wide automotive retail chain in New Hampshire before coming to GSA, is convinced that the stronger bumpers will save on maintenance costs.

"Going to a 5-mph bumper may exclude some manufacturers, like Chrysler Corp. , which no longer produce that type of bumper," Mitchell said.

Ford Motor Co. is installing 5-mph bumpers on all its cars, while General Motors Corp. is installing them only on selected models, using the 2 1/2-mph standard on the rest. American Motors Corp. is using only 2 1/2-mph bumpers.