An investigation by the Maryland attorney general into allegations of promotion abuses by senior state police officers concludes that the head of the agency, Superintendent Wilbert T. Travers Jr., has failed to correct a pattern of abuses revealed in 1981.

The report by Attorney General Stephen H. Sachs, which may be made public on Friday, does not implicate Travers as a participant in the promotional abuses, but strongly criticizes him for failing to stem them since taking over the agency in 1982, according to sources familiar with the report.

Travers could not be reached for comment.

Sachs' four-month investigation has centered on charges that senior commissioned officers in the state police have rigged promotional evaluation scores so that preselected individuals were granted promotions to the rank of second lieutenant and above. Among the senior officers on which the probe focused was Lt. Col. William T. Gerwig, chief of the logistical services bureau.

Gerwig refused to talk to investigators and in a subsequent court hearing he cited the police officers' bill of rights in arguing that he could be investigated only by another police officer. His contention was upheld today by a Baltimore County Circuit Court judge, according to Wayne McDaniel, an aide to Gov. Harry Hughes.

McDaniel said the Sachs report contains "no substantive proof" of the promotional abuse allegations because Gerwig's refusal to talk to investigators prevented "them from taking it far enough to say something has occurred." Sachs' report recommends that the investigation continue.

The report also recommends that the state police hire an outside consultant to devise a promotional system that will not be subject to manipulation, and urges the agency to freeze pending promotions.

Sources also said that Sachs has determined that black state police officers would have a solid case if they filed suit against the agency for racial discrimination.

This is the second time in less than four years that Sachs has probed state police promotional activities. Although the first investigation, in 1981, was never made public, a summary by Travers released in August 1982 found that some promotional evaluations "were not prepared in accordance with established Maryland State Police procedures."

"In some cases," that summary reported, "an officer's promotional potential rating was actually set before initiation of the prescribed evaluation process and some raters were directed to give predetermined scores to certain individual officers."

Sachs' latest report concludes that the system of manipulation continued after 1982, despite instructions from Hughes ordering Travers to "ensure that the promotional system is efficiently and fairly executed . . . . "

An irony of the investigations into state police promotional practices is that the agency's personnel rules allow the superintendent to promote anyone he wants, regardless of the promotional evaluation scores. Unlike managers in most state agencies, who must promote one of the top five candidates on lists whose rankings are determined by test scores, the state police superintendent can select anyone from the eligibility lists regardless of scores. Evaluation scores are based on interviews, background and experience and a "promotional potential rating."

Although Travers is criticized in the Sachs report for not putting an end to the promotional manipulations, he enjoys a good reputation among legislators and is said to have the full support of Hughes.

"But," concluded one legislator today, "if you're going to be in charge, you have to be prepared to be an s.o.b. sometimes. There needs to be a housecleaning up there."