Impreza 2.5 RS Sedan AWD F4-2.5L SOHC (2002)
Fuel Gauge Sender: Description and Operation
FUEL PUMP AND FUEL LEVEL SENSOR ASSEMBLY
FUEL PUMP
The fuel pump consists of a motor, impeller, pump casing, pump cover, check valve and filter. It is located in the fuel tank and combined with the fuel
level sensor into a single unit. The operation of this impeller type pump is very quiet.
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When the ignition switch is turned ON, fuel pump relay is activated. Then the motor operates to rotate the impeller.
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As the impeller rotates, fuel in a vane groove of the impeller flows along the fuel passage into the next vane groove by centrifugal force. When fuel
flows from one groove to the next, a pressure difference occurs due to friction. This creates a pumping effect.
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The fuel pushed up by rotation of the impeller then passes through the clearance between the armature and the magnet of the motor and is
discharged through the check valve.
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When the fuel discharge pressure reaches the specified level, the relief valve opens and excess fuel is released into the fuel tank. In this manner,
the relief valve prevents an abnormal increase in fuel pressure.
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When the engine and the fuel pump stop, spring force acts on the check valve to close the discharge port, so that the fuel pressure in the fuel
delivery line is retained.
FUEL LEVEL SENSOR
