Like a used car salesman hawking his wares on late-night television, President Carter urged consumers today to look over the new line of American models before they buy their next car.

Standing in the parking lot of the Ford Motor Company's assembly plant here, which served as the showroom for his pitch, Carter promised the auto industry and auto workers the full cooperation of the government in their competition with foreign automakers.

"Today, as president, I urge American consumers to go into showrooms around the country and test drive these new American cars," he said. "There is not a better built, safer, more durable or more efficient car today than these American models."

In a state wracked by unemployment because of the declining fortunes of the U.S. automobile industry, the president chose a bright spot to visit this morning to begin his first campaign trip to Michigan.

The Ford plant here employees 5,000 workers who, working on double shifts, are turning out 1,000 Ford Escort and Mercury Lynx models a day.

Ford executives, of course, were delighted by the visit. The new models, designed to compete with Japanese imports, go on sale Friday, and with rows of the new cars lined up behind him the president today certified them as First-rate, world-class" machines.

"It's kind of nice," Bill Harris, manager of Ford's corporate news department, said of the presidential visit. "But a resurgent auto industry in turn would boost the president."

Harris' analysis went precisely to the point of Carter's visit to the Ford plant. Nowhere in the country is the economy, as symbolized by the troubled auto industry and the layoffs of auto workers, more of an issue than in Michigan, a state the president lost in 1976. Republican presidential nominee Ronald Reagan, recognizing this, has already done his part to boost U.S. car sales. A few weeks ago he was in nearby Detroit, extolling the virtues of Chrysler's new K-car models.