TOKYO, JUNE 28 -- A former Nissan Motor Co. executive was elected today as president of Fuji Heavy Industries Co., giving Nissan effective control over the slumping manufacturer of Subaru cars.

Nissan, Japan's second-largest automaker, is Fuji's largest shareholder, with a 4.2 percent stake. Kimihide Takano, an analyst with Chemical Securities Co., said Nissan chose a typically Japanese way of exercising effective control over Fuji by sending an executive as president.

''This way, Nissan can obtain the same economic effects as acquiring the whole company,'' Takano said.

Fuji shareholders approved the selection of Isamu Kawai, former president of Nissan Diesel Motor Co., a subsidiary of Nissan Motor Co., during a meeting here.

Until about a decade ago, Subaru, Fuji's U.S. subsidiary that sells mostly four-wheel-drive models, was highly profitable, but its sales have plunged in the last few years. Analysts say the problem is weakness in its sales network.

Eighty percent of Fuji's 1989 sales of $4.3 billion came from automobiles. Its total sales were down 15 percent from the previous year, and Fuji ran up nearly $194 million in debt in the year. Meanwhile, sales of Nissan, Toyota Motor Corp., Honda Motor Co. and Mitsubishi Motors Corp. were booming in Japan and the United States.

Fuji previously had no seats on the board of Subaru of America Inc. because it did not fully own its U.S. subsidiary. It announced recently, however, that it had bought the rest of the shares in Subaru of America.