PURPOSE: To aim at improvements in an initial suction characteristic, by discharging such gas that deteriorates the initial suction characteristic out of the inside of a fuel feed system quickly, and unitizing a valve gear, being hermetically closed simultaneously with this system inside being filled up with fuel, with a discharge pressure pulsation absorber as one body.

CONSTITUTION: In the case where air and gas of fuel vapor or the like exist inside a pump unit, this gas passes through the circumference of a ball valve 5 being unitized with a discharge pressure pulsation absorbing damper part and is easily discharge to the inside of a fuel tank from an interconnecting hole, leading to the outside, installed in a damper casing at the low pressure side. After gas inside the pump unit is discharged out, the pump unit normally operates through liquid fuel and, after the pump unit is boosted for pressure, the ball valve 5 sticks fast to a valve seat 6 by means of a pressure differential between the inside and outside of the pump unit, whereby the discharge pressure absorbing damper part consisting of a diaphragm 7, a spring 10, the valve seat 6, etc., performs the same operation as the diaphragm and absorbs pulsation in the discharge. Thus, improvements in a favorable initial suction characteristic is made attainable with a simple structure.