Jewsbury's volley was a left-footed blast from the top of the penalty box after a corner kick ricocheted out to him. Until that point it appeared Portland would go down to another scoreless defeat after being shut out in its previous three games.
''I think the team is playing pretty well,'' Portland goalkeeper Troy Perkins said. ''I think we've really found ourselves. We just need to keep going.''
The Timbers (5-12-5) outshot Dallas 19-8, and maintained their aggressiveness down the stretch with temperatures in the mid-90s.
''Maybe they didn't deal with the heat as well as we did,'' said Portland general manager and interim coach Gavin Wilkinson.
The game marked the return of Shea, the star midfielder who had been benched for two straight games and hadn't played since being taken out of a July 18 game against San Jose.
Dallas dominated Portland 5-0 in their last meeting, on July 21 and Timbers general manager and interim coach Gavin Wilkinson accused his team of quitting.
Portland typically plays well at raucous Jeld-Wen Field, where all of its wins have come this season, and Dallas entered the match having won only one of 10 on the road.
Neither team had an exceptional start after the scoreless first half, where possession time was essentially even, though Portland outshot Dallas 9-4 before the break.
The Timbers were encouraged by the draw, believing they have righted their ship since the disaster in Dallas.
''I thought we deserved to win it,'' Wilkinson said. ''It feels like every mistake we make right now we get punished for.''
FC Dallas midfielder James Marcelin was making his return after being waived by Portland.
- FC Dallas
- Brek Shea