When electrical energy is supplied to the fuel pump, the motor in the pump runs and together with the impeller. This causes a pressure difference to occur on both sides of the impeller as there are many grooves around it. Then the fuel is drawn through the inlet port, and with its pressure increased, it is discharged through the outlet port. The fuel pump has a check valve to keep some pressure in the fuel feed hose even when the fuel pump is stopped. Also, the relief valve is equipped in the fuel pump, which releases pressurized fuel to the fuel tank when the outlet of the fuel pressure has increased up to 450-600 kPa (4.5-6.0 kgf/cm², 64-85 psi).
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1. Relief valve; 2. Brush; 3. Magnet; 4. Impeller; 5. Outlet port; 6. Check valve; 7. Armature; 8. Inlet port
When the impeller is driven by the motor, pressure differential occurs between the front part and the rear part of the blade groove as viewed in angular direction due to fluid friction. This process continuously takes place causing fuel pressure to be built up. The pressurized fuel is then let out from the pump chamber and discharged through the motor section and the check valve.
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1. Outlet; 2. Blade groove; 3. Inlet; 4. Flow clearance; 5. Impeller; 6. Motor shaft; 7. Vortex flow; A. Turning direction