| 摘要 |
A solenoid-operated pump for discharging fluid from a tank through a fluid discharge passage in a pump body has a directional control valve disposed in the fluid discharge passage. The directional control valve is normally urged to direct fluid flow through a fluid drainage passage branched from the fluid discharge passage and adapted for connection to the tank. The fluid drainage passage includes a restrictor which produces a fluid-pressure build-up in response to a change in viscosity of the fluid flowing therethrough, that is, when air is no longer contained in the fluid. The directional control valve is responsive to such pressure build-up to direct the fluid to flow through the fluid discharge passage.
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