A portable engine-driven system comprising an engine having an air intake passage, a fuel tank operatively coupled to the engine, a valve, and a pressure regulator. The valve may be coupled between the fuel tank and the air intake passage and configured to transition between a first position and a second position. The first position may allow fuel vapor to flow between the fuel tank and the air intake passage and the second position may inhibit the fuel vapor from flowing between the fuel tank and the air intake passage. The pressure regulator may be positioned in line between the fuel tank and the air intake passage.