Float Test

Make sure the fuel tank is less than half full.
Remove the fuel fill cap to relieve fuel tank pressure, then reinstall the cap.
Disconnect the fuel tank vapor recirculation turbe (A), and connecct a commercialy available vacuum pump/gauge, 0-30 in. Hg (A973X-041-XXXXX or Snap-On YA4000A or equivalent) to it.

Fig 1: Disconnecting The Fuel Tank Vapor Recirculation Tube, And Connect A Vacuum Pump To It
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Plug the line (B).
Apply vacuum to the fuel tank vapor recirculation tube.
- If the vacuum holds, replace the fuel tank vapor control valve (see FUEL TANK VAPOR CONTROL VALVE REPLACEMENT ).
- If the vacuum does not hold, the float is OK. Do the valve test.