Amtrak, announcing a sweeping personnel shakeup, pledged yesterday to improve service with better food, a more courteous staff and trains that run on time.

Amtrak President Alan S. Boyd, acknowledgeing that the system's record for running trains on time often has been "sad," said passengers will see continued and steady improvement."

"I don't want to give the impression that as of Oct. 1 there will be no more equipment malfunctions," he said. But he vowed that mechanical failures will be reduced monthly.

Improved service will not necessarily mean higher ticket prices, Boyd said. But, he added, there is "no way to put a cap on that unless we put a cap on inflation." Fuel prices have "gone out the window" this year, he said.

Amtrak's reorganization comes as increasing numbers of travelers are turning to the federally subsidized system because of the energy crisis and rising gasoline prices.

Sources reported Amtrack ridership had increased to 2.075 million in August, considerably above last August and the third month in a row Amtrack has hit the 2-million mark.

The sources indicated that the number of people unable to find seats on Amtrak trains was very high, perhaps as many as 1.8 million, including trains scheduled to be discontinued.

Amtrak has had 19.674 million passangers to date this year, a record for the company, the sources said.

Boyd reported to Amtrak's board that ridership revenues in August were an all-time high for that month, reaching $43.9 million, or 34 percent above the figure for August 1978.

The sudden popularity of rail service helped induce Congress to modify significantly a Transportation Department proposal earlier this year to reduce Amtrak service by 43 percent. The new legislation would cut service by 18 percent, eliminating six passenger trains.

A final version of the Amtrak legislation has been approved by the Senate and is expected to be passed by the House, Boyd said.

It would authorize $912.7 million in operating and capital funds in fiscal 1980, which begins Monday, $985 million in fiscal 1981 and $329 million for capital expenses only in 1982.

The shakeup, which involves creation of three new group vice presidents and appointment of five other vice presidents, also is a result of new legislation requiring Amtrak to plan ahead by giving the system spending authority for three years instead of one.

"Most of our excuses have been taken away" by the legislation, said one Amtrak spokesman; who asked not to be named.

M. L. Clark Tyler, who has been Amtrak's vice president for governmental affairs, was named to the newly created post of group vice president for passenger services and communications. Reparting to Tyler will be John V. Lombardi, vice president for passenger services; Carole Foryst, vice president for public affairs; and Lawrence D. Gilson, vice president for government affairs.

Thomas P. Hackney, who was in charge of Amtraks' equipment maintenance, was named new group vice president for operations and maintenance. He will have three vice presidents report to him: Robert A. Herman, operations; Robert F. Lawson, Chief engineer; and Frank D. Abate, chief mechanical officer.

Boyd said the new three-year authorization "will give Amtrak the resources it needs to rebuild the nation's rail passenger system."