Off-duty D.C. policeman Robert V. Frye sent gas station customers and employes scurrying for cover yesterday afternoon when he drew his .38-caliber police special, shouted, "Get Down!" and fired one shot outside an Anacostia service station that was holding his ailing Lincoln Continental hostage.

The way Frye told it to his superiors, he had indeed become angry over a $553 repair bill and less-than-satisfactory repairs on his car. But he said he drew his revolver, jumped behind a flower box on a Pennsylvania Avenue median strip and fired only after a customer at the station approached him with a gun.

Moments earlier, Frye and station manager Michael Pettrey, 31, had been embroiled in a shouting match about the quality of extensive repairs to the 1972 silver Continental, and Pettrey had returned Frye's personal check, locked the car in the garage and pocketed the ignition key.

"Your car will not leave this garage until I get cash," Pettrey said he hold the officer. "He was hollering and screaming and he wanted his money back."

Pettrey said he refused a refund on the repairs, but promised to honor the station's 90-day warranty on parts and labor. "I figured he was going to stop payment on the check," Pettrey said.

Frye, 29, who mans a desk in the planning and development division at police headquarters, later told department officials that he fired a shot at Jeffrey Neal Meggison, 23, a station customer, after Meggison drew a gun. Police spokesmen said no one was struck by the bullet. They refused to provide further details of the shooting incident.

Officers searched Meggison and found no gun, but charged him with possesion of marijuana. He was released last night on his own recognizance pending arraignment today.

No criminal or departmental charges were lodged against Frye, and the circumstances of the incident will be brought before the U.S. Attorney today for a determination, police officals said.

The rush hour drama reached its climax about 4:30 p.m. when Frye returned to the station after road testing his car, and complained that repair work had been inadequate.

The car was towed to the station, Pennsylvania Avenue Gulf, Monday. It would not start. On Tuesday, Pettrey said Frye gave him the greenlight to proceed with repairs. The estimate: $553.15.

Mechanic Boone Alley, 32, had determined the Lincoln needed an oil pump, a new distributor, a steering linkage and front disc brake pads. among other things. The repairs were made, and that night, Frye wrote out a check and drove off in his car.

He returned yesterday, grousing "that Pettrey. "He was real angry. He was shouting."

According to Pettrey, Frye said, "I'm a police officer. I have a gun and I'll get my car if you don't give it to me." The manager said Frye than threatened him with a police investigation.

"Right then, I realized if I didn't get the car, I wouldn't get the money for my check," said Pettrey.

A few minutes later, station employes said, Frye exchanged words with Meggison, who had just put $4 worth of gas into his white covertible, then shouted, "Get down, he's got a gun."

As employes and customers scrambled for cover, Frye ran to the median, drew his gun and fired.