Pedro Santos threaded a pass through four defenders and Kamara redirected the ball from the center of the box past Jon Kempin. Kamara leads the Crew (12-12-3) with 13 goals.
Zack Steffen picked up his seventh shutout without making a save. The Galaxy (6-13-5) had just five shots. It has the longest winless streak in MLS at nine games and has lost four straight on the road for the first time since 2008.
Daniel Steres of the Galaxy had a goal early in the first half negated by an offside call. Ashley Cole was sent off on a red card in the 18th minute, reducing the Galaxy to 10 men on the field.