Print DETROIT—Most of Ford Motor Co.'s most profitable assembly lines sit idle. Tens of thousands of partially built F-150s and other vehicles that could easily find buyers languish in parking lots. And the worst, CEO Jim Farley said, is yet to come. Ford told some dealers recently they won't get any meaningful amount of new inventory delivered until at least August. Many expect to be wiped out of what little they have left long before then. One Michigan dealer has created an emergency fund for its salespeople to draw from after that happens—likely sometime this month.