11 SERVICE TECH Vol.477 05-4

• The supply pump is primarily composed of the pump unit (eccentric cam, ring cam, two plungers), the SCV(suction control valve), the fuel temperature sensor, and the feed pump (trochoid type), and is actuated at1/1 or 1/2 the engine rotation.

• The two compact plungers in the supply pump are positioned symmetrically above and below on theoutside of the ring cam.

• The HP3 type supply pump employs the same SCV control method with the HP2 for fuel delivery quantity,reducing actuation load and surpressing the rise in fuel temperature. In addition, there are two types ofHP3 SCVs: the normally open type (the suction valve is open when not energized) and the normally closedtype (the suction valve is closed when not energized.)

11 HP3 Type Supply Pump Construction and Features

Suction Valve

Plunger

Ring Cam SCV

(Suction Control Valve)

Delivery Valve

Feed Pump

Fuel Temperature Sensor

External View

Cut Sample

12SERVICE TECH Vol.477 05-4

• The fuel is drawn by the feed pump from the fuel tank and sent to the SCV via the fuel filter. At this time, theregulating valve adjusts the fuel pressure to below a certain level.

• The SCV adjusts the required discharge quantity of the fuel sent from the feed pump. The fuel then enters theplunger via the suction valve, and is pumped to the rail via the delivery valve.

Components FunctionsFeed Pump Draws fuel from the fuel tank and feeds it to the plunger.Regulating Valve Regulates the pressure of the fuel inside the supply pump.SCV (Suction Control Valve) Controls the quantity of fuel that is fed to the plungers.

Pump UnitEccentric Cam Actuates the ring cam.Ring Cam Actuates the plunger.Plunger Draws and compresses fuel through reciprocal motion.

Suction Valve Prevents reverse flow of compressed fuel into the SCV.Delivery Valve Prevents fuel pumped from the plunger from back flowing out of the rail.Fuel Temperature Sensor Detects the fuel temperature.

22 Supply Pump Component Part Functions

33 Supply Pump Operation

1 Supply Pump Overall Fuel Flow

Filter

To Rail

Suction

Pump (Feed)

High-Pressure Fuel

Return

Injector Rail

From Pump

Delivery Valve

Plunger

Return Spring

SCV

Regulating Valve

Feed Pump

Fuel Suction Port

Suction

Fuel Filter

(With Priming Pump)

Fuel Tank

Camshaft

Return

Fuel Overflow

Suction Valve

13 SERVICE TECH Vol.477 05-4

The eccentric cam is attached to the cam shaft, and the ring cam is attached above the eccentric cam. Thereare two plungers (A and B) at positions symmetrical above and below the ring cam.

.

As the camshaft turns, the eccentric cam rotates in a decentered fashion, causing the ring cam to follow thismotion up and down. As a result the two plungers move reciprocally (The ring cam itself does not rotate).

2 Pump Unit (Eccentric Cam, Ring Cam, Plunger) Construction and Operation

Plunger A

Feed Pump

Plunger BEccentric Cam

Camshaft

Ring Cam

Ring Cam

Eccentric Cam

Camshaft

Plunger

14SERVICE TECH Vol.477 05-4

SERVICE TECH Vol.477 05-4 (Bi-monthly publication)Date of publication : April 20, 2005Editorial department : Service Department, DENSO

100% recycled papers are used in this magazine.

2005C

• The HP3 SCV employs a linear type solenoid valve. The HP3 differs from the HP2 ON/OFF (fully open/fullyclosed) control in that it controls the fuel flow quantity supplied to the plunger by controlling the time ofenergization from the engine ECU to the SCV.

• When current flows to the SCV, the armature moves in accordance with the energization time, causing thecylinder to move. As a result, the fuel path valve position changes, effectively controlling the fuel flow quantity.

• The normally open type SCV operation is shown below. The operation of the normally closed type SCV is theopposite of that detailed below.

Short SCV Energization TimeThe average current flowing through the solenoid is small, the cylinder is returned by the force of the

spring, and the valve opening is large. As a result, the fuel suction quantity increases.

Long SCV Energization TimeThe average current flowing through the solenoid is large, the cylinder is pressed out, and the valve

opening is small. As a result, the fuel suction quantity decreases.

3 SCV (Suction Control Valve) Operation

1

SCV

Cylinder

Feed Pump

Large Valve Opening

Cylinder

Plunger

Armature

2

Small Valve Opening

Cylinder

SCVFeed Pump

Cylinder