Feed Pump
• The feed pump is a four-vaned type that draws fuel from the fuel tank and discharges it to the pumping mechanism.
The rotation of the drive shaft causes the feed pump rotor to rotate and the vane to move by sliding along the inner surface of the casing (eccentric ring). Along with the rotation of the rotor, the pump draws fuel from the fuel tank, and discharges it to the SCV and the pumping mechanism. To keep the vane pressed against the inner circumference, a spring is provided inside each vane, in order to minimize fuel leakage within the pump.
Regulating Valve
• The purpose of the regulating valve is to control the feed pressure (fuel pumping pressure) sending fuel to the pumping mechanism. As the rotational movement of the pump increases and the feed pressure exceeds the pressure set at the regulating valve, the valve opens by overcoming the spring force, allowing the fuel to return to the suction side.
SCV: Suction Control Valve
• A solenoid type valve has been adopted. The ECU controls the duration of the current applied to the SCV in order to control the quantity of fuel drawn into the pumping mechanism. Because only the quantity of fuel required to achieve the target rail pressure is drawn in, the actuating load of the supply pump decreases, thus improving fuel economy.
SCV ON
– When current is applied to the coil, it pulls the needle valve upward, allowing fuel to be drawn into the pumping
mechanism of the supply pump.
SCV OFF
– When current is no longer applied to the coil, the needle valve closes and stops the suction of fuel.
Pumping Mechanism (Plunger, Inner Cam, Roller)
• The pumping mechanism is made up of the plunger, inner cam, and roller, and it draws in the fuel discharged by the feed pump and pumps it to the rail. Because the drive shaft and the inner cam have an integral construction, the rotation of the drive shaft directly becomes the rotation of the inner cam.
• Two plunger systems are arranged in series (tandem type) inside the inner cam. Plunger 1 is situated horizontally, and plunger 2 is situated vertically. Plunger 1 and plunger 2 have their suction and compression strokes reversed (when one is on the intake, the other is discharging), and each plunger discharges twice for each one rotation, so for one rotation of the supply pump, they discharge a total of four times to the rail.
Delivery Valve
• The delivery valve, which contains two valve balls, delivers the pressurized fuel from plungers 1 and 2 to the rail in alternating strokes. When the pressure in the plunger exceeds the pressure in the rail, the valve opens to discharge fuel.
Fuel Temperature Sensor
• The fuel temperature sensor is installed on the fuel intake side and utilizes the characteristics of a thermistor in which the electric resistance changes with the temperature in order to detect the fuel temperature.
Check Valve
• The check valve, which is located between the SCV (Suction Control Valve) and the pumping mechanism, prevents the pressurized fuel in the pumping mechanism from flowing back into the SCV.
Check Valve Open
– During fuel suction (SCV ON), the feed pressure opens the valve, allowing fuel to be drawn into the pumping mechanism.
Check Valve Closed
– During fuel pumping (SCV OFF), the pressurized fuel in the pumping mechanism closes the valve, preventing fuel from flowing back into the SCV.
