Twenty-three white St. Louis firefighters have sued the city, claiming a coming examination for promotion to captain favors black applicants. The suit seeks an order to block the city from giving the test until the claims of the plaintiffs are considered. The suit alleges the department has violated the rights of the white claimants by providing black applicants with better opportunities for promotion. It also claims the planned exam is inadequately job related and was purchased from an outside firm without taking bids.