With the new fiscal year less than a month away, and anxious federal agencies awaiting their money, the Senate Appropriations Committee yesterday finally got around to the first of 13 major appropriations bills.

But that serious business was quickly pushed aside by an extraordinary outpouring of rage, and a few insults, involving Sens. Thomas F. Eagleton (D-Mo) and Lowell P. Weicker Jr. (R-Conn.).

Customary senatorial courtesy and decorum were forgotten completely as Eagleton and Weicker went at it in a feverish fashion that left their colleagues and spectators stunned.

The fight was over an Eagletton amendment to prohibit the Environmental Protection Agency from using funds in the bill to test and certify a new small car the Soviet Union plans to sell here.

Eagleton said importation of the Lada, as the Russian car is called, would send "the wrong message" to the Soviet Union and to hard-pressed U.S. farmers and auto workers, victims respectively of the Soviet grain embargo and increasing foreign competition.

Weicker complained that the amendment was too selective. He proposed that it be changed to stop all federal spending on trade between the United States and the Soviet Union.

"If we are going to respond to the Soviet Union, let's do it right across the board," Weicker said. "It would cover everything. We are all in the same boat."

When Weicker was unable to tell the committee what imports would be halted by an altered amendment, Eagleton shouted, "You don't know. That's embarassment."

"I'm just saying 'no more,'" Weicker responded. "I don't believe in picking on our farmers and here we have aRepublican presidential candidate who wants to get tough with the Russians, but to end the grain embargo. That's nonsense!"

"The truth is, Weicker doesn't know what it [his proposal] would do," Eagleton said. "The truth is that Lowell Weicker wants to give us more lectures. You talk about a corner of hot air!" You are preeminently ridiculous most of the time!"

The committee voted 9 to 7 to table Weicker's amendment, then adopted the Eagleton amendment, 11 to 4. Although the White House opposes the rider, saying it would intrude on presidential policymaking, it is expcted to win full congressional approval.

The flap occured during consideration of the money bill for housing, draft registration, environmental protection, space sciences, veterans and other programs. The is the first of 13 must be approved before Congress adjourns.

Unusual delays -- among them debate over budget resolutions and Carter's resubmission of his fiscal 1981 budget -- have thrown Congress off its usual appropriations timetable and have raised doubts about completing all bills before adjournment next month.

The House has approved 10 of the 13 measures and sent them on to the Senate, where the Appropriations Committee plans to move them to the floor as quickly as possible.

Committee Chairman Warren G. Magnuson (D-Wash.) intends to have two bills done this week and at least four more completed a week from now.

The first part of Magnuson's goal was achieved yesterday with passage of the $70.1 billion housing measure and subsequent adoption of a $12 billion bill for energy and water resources programs.

With the House about two months behind and the Senate at least a month behind usual schedules, prospects have increased that many agencies will be forced to enter the new fiscal year with "continuing resolutions" that authorize expenditures at this year's levels and provide for no new programs.

Magnuson predicted yesterday that his committee could complete much of its work in the next two weeks and send the money bills to the floor "if everybody stays awake."