| 摘要 |
A positive displacement type pump for use in a fuel system of an internal combustion engine having a pump housing that includes a pump chamber and a vapor vent valve to allow vapor to flow out of the pump chamber. The vent valve includes a valve seat, a valve and a spring biasing the valve away from the valve seat. During pump operation, the liquid fuel flow pressure within the pump chamber is great enough to seat the valve and prevent fuel from escaping through the vapor vent valve. However, if the internal pressure drops due to a loss of pumping pressure caused by the ingestion of air or vapors, the vent valve automatically opens to allow vapor or air flow through the pump with a resultant cooling effect on the pump assembly.
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