Tesho Akindele was the hero for FC Dallas, with his late goal lifting the Western Conference high-flyers past reigning MLS Cup champions Los Angeles Galaxy 2-1.
With four minutes of regulation time remaining at Toyota Stadium in Frisco on Saturday, Akindele received a diagonal pass from Mauro Diaz just outside the penalty area and curled the ball beyond Galaxy goalkeeper Jaime Penedo.
Akindele's match-winner ensured Dallas stayed level with Vancouver Whitecaps (20 points), who top the standings on goal difference after accounting for Philadelphia Union 3-0.
Gyasi Zardes, who met Stefan Ishizaki's 59th-minute corner, shrugged off his opponent and glanced a header past keeper Dan Kennedy with relative ease.
Akindele then scored his fourth goal of the season to extend Dallas' unbeaten run to four matches.
The Sounders went into the half-time break level at 1-1 thanks to Dempsey, who cancelled out Kei Kamara's opener.
Federico Higuain restored the Crew's lead four minutes into the second half, before Kamara doubled the home team's advantage just shy of the hour mark.
Dempsey pulled a goal back from close range in the 75th minute but Crew held on for all three points to jump up to third in the Eastern Conference, with the fourth-placed New York Red Bulls scheduled to play New York City on Sunday.
Elsewhere, beaten CONCACAF Champions League finalists Montreal Impact's return to MLS action did not go according to plan, losing 2-1 at home to Portland Timbers.
