ATLANTIC CITY, N.J. (AP) _ A radio station promotion grinded to halt after three keys started the same car, leaving station officials bewildered and unsure of what to do.

The problems started when WMGM-FM offered to give a car to whoever selected one key out of 80 that would start the engine.

On Saturday, one contestant put a key in the ignition of the 1987 Dodge Daytona and started the engine. Then another did the same thing. Then a third.

''I was dumbfounded,'' said Steve Gural, the station's sales manager. ''I never, never, ever expected more than one key to start the car.''

Later, none of the three keys would start the car, and the station locked up the vehicle, which might have had a faulty lock.

Station officials still hadn't decided whether they would hold another drawing or give the car to one of the three contestants.

The strange happenings occurred at a picnic to which WMGM invited the 80 listeners who had won the right to pick one of the keys.

Gural said some contestants already have protested the way the contest was run and threatened to sue the radio station.

Sales officials at the Chrysler-Plymouth dealership where the car was picked up said they suspected some loose tumblers in the car's ignition lock allowed more than the one key to start the car.

The car was donated by the Chrysler Corp.