John E. Granfield, a 16-year member of the Fairfax County Police Department who has handled tasks ranging from school safety programs to budgets, was named acting chief of the force yesterday, an appointment that makes him the likely successor to retiring Chief Carroll D. Buracker.

Granfield, 40, will assume command Friday from Buracker, 42, who is becoming a private consultant. He has headed the 800-officer department, the largest local police force in Virginia and the fourth largest in the Washington area, since June 1981.

Granfield, who joined the Fairfax police after leaving the military in 1969, called yesterday's announcement "certainly the capping of this career -- that's for sure."

His promotion, coming four months after he was promoted to deputy chief for operations, was widely viewed as a signal that he is in line to become the next chief.

County Executive J. Hamilton Lambert made the appointment in a one-line memo to Granfield. The officer, who lives with his wife and three children in Oakton, currently earns $55,271. His salary will not rise unless he is named permanent chief, county officials said.

It has been a technique of Lambert's to promote heads of agencies to the acting position for several months before asking the Board of Supervisors to make their appointments permanent.

Deputy County Executive Richard King said yesterday a permanent chief would likely be named by July 1.

A gregarious administrator, Granfield said it "would be presumptuous" to speculate on who will be made permanent chief. "It's an acting position, and I'm certainly not making any changes," he said. "My philosophy and Col. Buracker's are very close."

When Buracker announced his intention to retire last December to start a security-consulting business, county officials said the new police chief would be promoted from within the department.

No search is being conducted for a new chief, and officials say the only other person seriously considered for the chief's position has been Lt. Col. Alan Barbee, 42, the deputy chief for administration.

Buracker, after three years in the chief's position, is being paid $66,953, and said when he announced his intention to step down that his retirement benefits were part of what motivated him to leave the county government.

Buracker aggressively pushed the department into high-technology methods of fighting crime during his tenure. The county police have begun to use computers routinely to track and predict crime; acquired two helicopters with infrared detection gear and soon will install state-of-the-art dispatching equipment, including computer terminals in all patrol cars.

Granfield has held a wide range of positions during his time at the department, including K-9 officer, supervisor of the school safety program, commander of the Mount Vernon District, commander of community relations, and most recently commander of the operations division, with overall responsibility for the day-to-day running of the patrol and investigative sections of the department.