Ford Motor Co. posted a 7% increase in January U.S. sales, a promising start to a year in which investors expect Chief Executive Jim Hackett to show results from his turnaround plan.

The Detroit auto maker is feeling pressure to boost its cash flow as concerns about the company’s investment-grade rating and its ability to pay its current dividend are on the rise. Mr. Hackett, 20 months into his tenure, has promised to cut expenses and restructure floundering businesses overseas, while populating U.S. showrooms with more high-margin...