Fuel Pump - Subaru SVX 1992 Manual

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Table of Contents

3 . Fuel Pump

A: CONSTRUCTION

The fuel pump is an impeller type . It is built into the fuel

tank together with the fuel meter unit to provide quiet

operation . The fuel pump consists of a motor, impeller,

pump casing, pump cover, relief valve, check valve and

pump filter .

Fuel return hose

Fuel delivery hose

Relief valve

Discharge G~

~- Pump casing

Flow passage

B: OPERATION

1) When the engine starts, fuel pump relay activates .

This operates the motor to rotate the impeller .

2) Fuel entering a vane groove of the impeller flows

along the fuel passage and into the next vane groove by

centrifugal force . During the time fuel flows from one

groove to the next, a pressure differential is produced

by friction of the flow.

3) Thus, fuel pressure increases while the action is

described in step 2) above is repeated, and fuel is

discharged from the pump casing . Fuel under pressure

then passes through the clearance between the arma-

ture and the magnet and is discharged from the fuel

4) As fuel discharge pressure reaches the specified

value, the relief valve opens. This discharges fuel under

pressure into the fuel tank. Fuel from the fuel tank then

returns to the suction port and passes through the fuel

pump . This action of fuel flow is repeated . In this

manner, the relief valve prevents an abnormal increase

in fuel pressure .

5) When the engine and fuel pump stop, spring force

acts on the check valve to close the discharge port so

that fuel pressure remains in the fuel delivery line .

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