A fuel vent valve is not shut improperly by the flow of fuel vapor. The fuel vent valve also prevents fuel from spilling out from filler neck during filling of a fuel tank. The fuel vent valve includes a casing having a vent space, a float and a vent device which can be moved up and down. The vent device includes an upper valve member, which shuts and opens a communication passage. The upper valve member is located above the float. A breathing hole and an outer wall of the valve device form a restricted passage. When the fuel level reaches a first predetermined level and the valve device rises, the restricted passage increases the flow resistance to restrict the flow of fuel vapor from the communication passage to the outside of the fuel tank. When fuel level reaches a second predetermined level and the valve device rises further, the upper valve member closes the communication passage.

 
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> Method and system for improving a part's resistance to stress induced failure

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