They used to talk of "locomotives" and of a "convoy." But now the togetherness metaphors have been discarded. "Up to Germany" is the slogan for the economic summit that will bring President Carter together with the leaders of six other industrialized countries in Bonn this weekend.

While there is widespread recognition of the need for concerted action, the Carter administration is too burdened by problems of energy and inflation to play the leadership role customary for the United States. No other country is in position to get out front except, just possibly, West Germany.

The need for coordinated economic action arises from a general sluggishness. At present the advanced countries show a composite economic growth of less than 3 percent annually.

That is not enough for full employment in the United States, Japan, Germany, France or Italy. Neither does it yield the revenues for social improvements desperately needed in parts of all the developed countries and throughout Japan. Still less does it afford the surplus required to give aid to the poorest countries.

But formidable obstacles stand in the path of a new economic spurt. There is the grave danger of inflation and - through the agency of measures to contain inflation - a new recession. Moreover, two of the developed countries - Germany and Japan - depend heavily on growth through exports. So stimulus must be managed in a way that does not foster a push toward protectionism in other countries.

A year ago the Carter administration entertained the theory that all the advanced countries could be pulled along if the three most powerful economies acted as locomotives. At the London economic summit the United States, Germany with Japan signed on to ambitious growth targets.

But the Germans and Japanese, more concerned to check inflation than expand their economies, fell way below the appointed targets. Hence the continued slow growth in all the industrialized countries.

Briefly there was talk of moving from the "policy of locomotives to the policy of convoy." But that meant everyone would have to advance slowly. For four countries - Britain, France, Italy and Canada - are still coping with inflation and balance-of-payments deficits. The best they can do is avoid measures that constrain internal growth and cut down foreign trade. Even to do that they will need the promise of better markets in other industrialized countries.

The United States is in exceptionally poor position to help. Inflation is on the rise, and the emphasis in Washington is more on economic restraint than on stimulus. Despite repeated promises, moreover, the Carter administration has still not pushed through the Congress a bill limiting oil imports.

Si the United States is highly vulnerable to the charge that it is importing inflation and weakening confidence in the dollar by failure to control energy imports. That charge is particularly dear to the Japanese. The weakness of the dollar has resulted in an appreciation of the yen, which means higher costs for Japanese exports and continuing recession in some Japanese industries. Prime Minister Takeo Fukuda has been arguing that, despite huge trade surpluses, Japan cannot open its markets and stimulate its economy unless the United States first takes action to hold down oil imports and stabilize the dollar.

That leaves everything up to the Germans. Chancellor Helmut Schmidt has curtailed inflation at a fairly low cost in unemployment. He thinks the German economy is coming back, and is loath to change a mix which is highly favorable to his own Social Democratic Party.

But the opposition Christian Democrats have come out strongly for a tax cut to stimulate business. The chancellor's coalition partners - the Free Democrats - have taken up the tax-cut idea. Accordingly, the chancellor may be obliged to go along.

If he does, he will demand that the United States promise to do something about energy, that Japan promise to open its market and stimulate growth, and that other countries promise to avoid protectionist measures. So a forward step by Germany could produce a package of promises.

But it remains unclear whether Germany will take the first step, whether the promises would be kept, or whether, even if they were, they would do much good. So the question to be asked of the Bonn summit this weekend is whether seven horrendously busy men can deal effectively with deep-seated economic problems requiring long-term policies at a meeting of less than 48 hours.