The teams have split the first two games of the three-game series with the rubber match on Sunday.
Jonah Heim and Corey Seager added solo home runs for the Rangers
Daulton Varsho hit a solo home run for Toronto.
Dunning (6-1) allowed two runs, six hits and one walk in six innings.
Toronto right-hander Trevor Richards (0-1) allowed three runs, three hits (two home runs) and one walk in three-plus innings as the opener in a bullpen day.
Toronto scored once in the first. Bo Bichette doubled to right with two out and scored on Vladimir Guerrero Jr's single to left. Guerrero took second on the throw home. He was thrown out by Adolis Garcia when he tried to score on Varsho's single to right.
Texas took a 3-1 lead in the second. Garcia led off with a walk and Jung hit a blast to right for his 14th homer of the season. Heim followed with his eighth homer of the season, a drive to right.
Varsho hit his 12th homer of the season, a drive to right, with one out in the top of fourth.
Bowden Francis replaced Richards after Garcia's leadoff single in the home fourth, Jung's shot down the right-field line was first ruled a home run, but the call was changed to a foul ball after a review.
Seager hit a one-out shot to right against Yimi Garcia for his 10th home run of the season with one out in the home seventh. Nathaniel Lowe and Garcia followed with singles and Adam Cimber took over on the mound and ended the inning with a double-play grounder by Jung.
Josh Sborz worked the seventh and eighth for Texas, allowing only a single.
Will Smith pitched around singles to Guerrero and Matt Chapman to earn his 12th save of the season.
--Field Level Media