Leaders of the world's largest industrial democracies ended three days of intensive discussion of global problems today with statements of renewed unity and common purpose but with no new answers to a staggering array of international problems.

East-West political and military confrontations, the high state of Mideast tension, continuing warfare between Iran and Iraq, internal struggles in Central America, battles over Cambodia, fighting in Afghanistan, other dangerous or bloody situations and the global economic situation were discussed by heads of government or their foreign ministers.

Asked if summit leaders had done anything that could ameliorate world problems, Secretary of State George P. Shultz pointed to Sunday night's joint statement on arms control in the political field and today's declaration in the economic area.

All of this, Shultz said, "presents a picture of a group of countries that are deeply concerned, capable, have resources, will use them, know how to use them and are determined.

"I think it is a very strong message, both to ourselves and our own people and the people around the world about the kind of leadership that the world is going to get from the countries represented."

Italian Foreign Minister Emilio Colombo, answering a similar question, said the summit's principal accomplishment in the political field was "verification of certain facts and gravity of these facts" for all of the leaders concerned and a determination flowing from this realization that unified action is essential.

The pronouncements sounded as if the leaders discovered anew in this colonial village what Benjamin Franklin said in 1776: "We must all hang together, else we shall all hang separately."

Of various global problems discussed, the East-West confrontation, especially on nuclear arms, was given by far the greatest time and attention, most of which was consumed in negotiating and drafting the joint statement on arms control.

The difficult problem, several officials said today, was drafting a paper broad enough to win approval of France, which is not a member of the NATO military command and has a mind of its own on most international questions, and of Japan, which had not been associated with joint statements on western security.

That this could be done at all, despite strains involved, was considered a significant achievement.

Nobody was under the illusion, though, that the statement will have much practical effect on U.S.-Soviet negotiations in Geneva on European-based nuclear missiles or parallel negotiations there on long-range nuclear weapons.

The statement, its authors acknowledged, was aimed as much at international public opinion, especially that in allied countries, as at Moscow.

The leaders also discussed a meeting between President Reagan and Soviet leader Yuri V. Andropov, but there was no indication that Reagan has changed his noncommittal and lukewarm view of such a summit.

Late this afternoon, Reagan met West German Chancellor Helmut Kohl in a special meeting to discuss Kohl's visit to Moscow July 4 to 8. It will be the first major visit by a western leader to the new Soviet chief.

Private dinner talk Sunday night among the leaders concentrated on the Mideast situation, but only the sketchiest reports of the discussion were available. Colombo said the six other nations had agreed to support Shultz' recent Mideast peace mission by making new approaches of their own to Syria urging a Syrian withdrawal from Lebanon.

Due to the unusually high state of tension in the Mideast, including continuing Israeli alarm about Syrian troop movement, Shultz kept one eye warily cocked on that region.

He said tonight that on the basis of U.S. intelligence reports, "the level of tension seems to have subsided a little bit." Nonetheless, U.S. officials are anything but relaxed about the continuing trouble in and around Lebanon.

A consensus emerged, a participant said, that overtures from Iran about improved relations should be answered positively. And consensus was reported on reconsidering sanctions against Poland following the visit to Warsaw of Pope John Paul II next month.

For all of the talk, the problems remain--most of them probably until the next annual summit and beyond.