Diesel Engine Troubleshooting

HP3 Supply Pump Component Part Functions

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pic1 38 HP3 Supply Pump Component Part Functions

Feed Pump
• The trochoid type feed pump, which is integrated in the supply pump, draws fuel from the fuel tank and feeds it to the two plungers via the fuel filter and the SCV (Suction Control Valve). The drive shaft actuates the outer/inner rotors of the feed pump, thus causing the rotors to start rotating. In accordance with the space that increases and decreases with the movement of the outer and inner rotors, the feed pump draws fuel into the suction port and pumps fuel out the discharge port.

pic1 39 HP3 Supply Pump Component Part Functions

Regulating Valve
• The regulating valve keeps the fuel feed pressure (discharge pressure) below a certain level. If the pump speed increases and the feed pressure exceeds the preset pressure of the regulating valve, the valve opens by overcoming
the spring force in order to return the fuel to the suction side.

pic1 40 HP3 Supply Pump Component Part Functions

Suction Control Valve (SCV)
. In contrast to the HP2, the SCV for the HP3 supply pump is equipped with a linear solenoid valve. The fuel flow volume supplied to the high-pressure plunger is controlled by adjusting the engine ECU supplies power to the SCV (duty ratio control). When current flows to the SCV, the internal armature moves according to the duty ratio. The armature moves the needle valve, controlling the fuel flow volume according to the amount that the valve body fuel path is blocked. Control is performed so that the supply pump suctions only the necessary fuel quantity to achieve the target rail pressure. As a result, the supply pump actuation load is reduced.

. There are two types of HP3 SCV: the normally open type (the suction valve opens when not energized) and the normally closed type (the suction valve is closed when not energized). The operation of each type is the reverse of that of the other.

. In recent years, a compact SCV has been developed. Compared to the conventional SCV, the position of the return
spring and needle valve in the compact SCV are reversed. For this reason, operation is also reversed.

Normally Open Type
– When the solenoid is not energized, the return spring pushes against the needle valve, completely opening the fuel passage and supplying fuel to the plungers. (Total quantity suctioned ¨ Total quantity discharged)
– When the solenoid is energized, the armature pushes the needle valve, which compresses the return spring and
closes the fuel passage. In contrast, the needle valve in the compact SCV is pulled upon, which compresses the return spring and closes the fuel passage.
– The solenoid ON/OFF is actuated by duty ratio control. Fuel is supplied in an amount corresponding to the open surface area of the passage, which depends on the duty ratio, and then is discharged by the plungers.

pic1 41 HP3 Supply Pump Component Part Functions

Duty Ratio Control
– The engine ECU outputs sawtooth wave signals with a constant frequency. The value of the current is the effective
(average) value of these signals. As the effective value increases, the valve opening decreases, and as the effective value decreases, the valve opening increases.

pic1 42 HP3 Supply Pump Component Part Functions

When the SCV Energized Duration (Duty ON Time) is Short
– When the SCV energization time is short, the average current flowing through the solenoid is small. As a result, the needle valve is returned by spring force, creating a large valve opening. Subsequently, the fuel suction quantity increases.

pic1 43 HP3 Supply Pump Component Part Functions

pic1 44 HP3 Supply Pump Component Part Functions

When the SCV Energized Duration (Duty ON Time) is Long
– When the energization time is long, the average current flowing to the solenoid is large. As a result, the needle
valve is pressed out (in the compact SCV, the needle valve is pulled), creating a small valve opening. Subsequently, the fuel suction quantity decreases.

pic1 45 HP3 Supply Pump Component Part Functions

pic1 46 HP3 Supply Pump Component Part Functions

Normally Closed Type
– When the solenoid is energized, the needle valve is pressed upon (in the compact SCV, the cylinder is pulled upon) by the armature, completely opening the fuel passage and supplying fuel to the plunger. (Total quantity suctioned ? Total quantity discharged)
– When power is removed from the solenoid, the return spring presses the needle valve back to the original position, closing the fuel passage.
– The solenoid ON/OFF is actuated by duty ratio control. Fuel is supplied in an amount corresponding to the open
surface area of the passage, which depends on the duty ratio, and then is discharged by the plungers.

pic1 47 HP3 Supply Pump Component Part Functions

Duty Ratio Control
– The engine ECU outputs sawtooth wave signals with a constant frequency. The value of the current is the effective
(average) value of these signals. As the effective value increases, the valve opening increases, and as the effective value decreases, the valve opening decreases.

pic1 48 HP3 Supply Pump Component Part Functions

When the SCV Energized Duration (Duty ON Time) is Long
– When the energization time is long, the average current flowing to the solenoid is large. As a result, the needle
valve is pushed out (in the compact SCV, the needle valve is pulled), creating a large valve opening. Subsequently,
the fuel suction quantity increases.

pic1 49 HP3 Supply Pump Component Part Functions

When the SCV Energized Duration (Duty ON Time) is Short
– When the energization time is short, the average current flowing through the solenoid is small. As a result, the needle valve is returned to the original position by spring force, creating a small valve opening. Subsequently, the fuel suction quantity decreases.

pic1 50 HP3 Supply Pump Component Part Functions

Pump Unit (Eccentric Cam, Ring Cam, Plunger)
• The eccentric cam is attached to the camshaft and the ring cam is installed on the eccentric cam. There are two plungers at positions symmetrical above and below the ring cam.

pic1 51 HP3 Supply Pump Component Part Functions

• Because the rotation of the camshaft makes the eccentric cam rotate eccentrically, the ring cam follows this and
moves up and down, and this moves the two plungers reciprocally. (The ring cam itself does not rotate.)

pic1 52 HP3 Supply Pump Component Part Functions

Delivery Valve
• The delivery valve for the HP3 has an integrated element and is made up of the check ball, spring, and holder. When the pressure at the plunger exceeds the pressure in the rail, the check ball opens to discharge the fuel.

pic1 53 HP3 Supply Pump Component Part Functions

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.

pic1 54 HP3 Supply Pump Component Part Functions

Written by Jack

March 6th, 2019 at 7:47 am

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