Wimmer drove his Chevrolet Monte Carlo to his fifth career win and first since last November at Homestead-Miami.
Keller settled for second place, with Scott Riggs finishing third to regain the lead in the Busch series standings. David Green had been on top coming into this race but spun on the final lap and placed 12th.
Riggs has a two-point advantage over Green with 13 races remaining. Keller and Ron Hornaday, who came in seventh, are 50 points back.