The jury today began deliberating federal price fixing charges against seven cut-rate gasoline companies, taking with them a shopping cart full of documents, dozens of huge cardboard diagrams and notes on three months of testimony.

Asst. U.S. Attorney Rodney O. Thorson urged the jurors not to be overwhelmed by the mass of complex price and telephone records in evidence, but instead to view the case in its entirety.

"This was collusive, collective undertaking . . . to disrupt the free enterprise system and impose upon it restraints," he said.

The government charged the existence of a conspiracy between 1967 and 1974 to fix prices on 17 billion gallons of gasoline worth $4 billion sold in the District of Columbia and six states: Maryland, Virginia, Delaware, Pennsylvania, New York and New Jersey.

The defendants are Continental Oil Co., Amerada Hess Corp., Ashland Oil Inc., Kayo Oil Co., Crown Central Petroleum, Meadville Corp. and the Petroleum Marketing Corp. (PMC). Also on trial are their trade association, the Society of Independent Gas Markets of America (SIGMA) and SIGMA's executive director, Robert R. Cavin.

Defense atorneys mustered charts and diagrams to back their claims that price fluctations were too frequent, too different among the companies and the result of too many factors for any conspiracy to have existed.

"There's no way there's going to be an agreement that requires these people to change their prices everyday," said Meadville attorney Philip M. Cohan in his closing argument Wednesday.

Cavin said outside the courtroom that independent firms are now distributed more or less evenly across the country. They market gasoline under a variety of brand names and through affiliates, subsidiaries and contractors.

Some of them involved in this case include Hess, from Amerada Hess; Red-Head, Pay-Less, Bi-Lo, Hi-Fy and Rotarv, from Ashland; Conoco, from Continental; Kayo, Merit, Saveway and Martin, from Meadville; and Scott, from PMC.