A former CIA official and two business associates pleaded guilty yesterday to federal criminal charges involving a scheme to export $5 million worth of diesel engine manufacturing equipment to the Soviet Union.

Paul Sakwa, 59, a former CIA and State Department officer who is now a Washington-based business consultant, and Stephen G. Carter, 46, a Chicago business executive, entered guilty pleas in U.S. District Court in Alexandria to single felony counts of violating U.S. export regulations.

Exports of machinery to the Soviet Union's large Kama River Truck Complex have been barred by U.S. Commerce Department regulations since 1980 in response to Soviet military moves in Afghanistan. The plant is believed to produce equipment used by Soviet forces.

In addition, Gerald F. McCall, 51, a Toronto businessman, pleaded guilty to a single misdemeanor count of conspiring to submit a false declaration to the U.S. Customs Service in connection with the scheme. The declaration, which was never filed, would have falsely named a Western European country, rather than the Soviet Union, as the ultimate destination for the equipment.

The three men entered their guilty pleas yesterday morning, 35 minutes before they were scheduled to go on trial. As part of a plea agreement, Assistant U.S. Attorney Joseph J. Aronica said the government would drop its earlier 11-count indictment, which was returned by a grand jury Jan. 4.

Judge Richard L. Williams set sentencing for April 1. Sakwa and Carter could be sentenced to up to five years' imprisonment and substantial fines. According to prosecutors, the fines may be as high as five times the value of the equipment intended for export--a sum that could amount to millions of dollars. McCall could receive up to a year's imprisonment and a $1,000 fine.

Mark H. Tuohey III, an attorney for Sakwa, later characterized the charge to which the guilty plea was entered as a "technical violation" and said that Sakwa did not believe at the time the deal was being arranged that he could be violating export rules. "He did not have any intention to violate the law," Tuohey said.

Sakwa, a CIA employe from 1952 to 1962, gained prominance in 1973 when he opposed President Nixon's choice of William E. Colby to head the CIA, criticizing Colby's performance as CIA station chief in Saigon in the early 1960s. Sakwa was a State Department research officer until 1964 when he became a private consultant.

Michael H. Salsbury, a lawyer for Carter, declined to comment. Attorneys for McCall could not be reached for comment.

The charges to which the three men pleaded guilty entailed a complex series of business negotiations, including tape-recorded telephone conversations with undercover investigators posing as prospective purchasers of the equipment. The men were charged with making arrangements to try to sell the machinery to a fictitious company, set up by investigators. The fictitious firm purported to seek to export it to the Soviet Union.