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| Illustration 1 | g03842226 |
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(1) Engine ECM
(2) High Pressure Fuel Pump (3) Common Rail Manifold (4) Injectors | |
The fuel system is a common rail fuel system. This common rail system not only complies with strict emission regulations the system enables multiple, high-pressure injections that do not vary with engine RPM.
The system is an electronically controlled fuel injection device with a high-pressure fuel pump (2) that pressurizes the fuel rail manifold (3).
The ECM controls the amount from the injectors, the timing of injection and the pressure in the common rail manifold. This results in fuel always being injected under ideal conditions, which suppresses the hallmark of a diesel engine, the black smoke during takeoff and acceleration. So there is less smoke, cleaner with a higher output of power.
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| Illustration 2 | g03842290 |
| (1) PCV (Pre-Stroke Control Valve) | |
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| Illustration 3 | g03842303 |
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(1) PCV (Pre-Stroke Control Valve)
(2) Housing (3) Camshaft (4) Delivery Valve (5) Plunger (6) Tappet (7) Feed Pump (8) Cam | |
The supply pump is equivalent to previously used injection pumps and the pump delivers fuel to the rail at a pressure more than double that of previous pumps. The supply pump consists of a feed pump (7), a PCV (Pre-Stroke Control Valve) (1), and a delivery valve (8).
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| Illustration 4 | g03842329 |
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(1) Outer Rotor
(2) Inner Rotor (3) Suction Port (4) Discharge port (5) Camshaft | |
The feed pump sucks up fuel filtered by the fuel filter and supplies fuel to the pump unit.
The feed pump is a Trochoid pump with an inner rotor (2) and an outer rotor (1), geared elliptically, the inner rotor is driven by the camshaft (5) and drives the outer rotor in the same direction. In the process, the volume of the part enclosed by the teeth of the rotor changes and pumps the fuel.
PCV (Pre-Stroke Control Valve)
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| Illustration 5 | g03842362 |
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(1) Solenoid
(2) Armature (3) Pushrod | |
The PCV adjusts the amount of fuel discharged from the supply pump to adjust rail pressure. The amount of fuel discharged from the supply pump to the rail is determined by the energize timing of the PCV.
The valve is opened and closed by the ON/OFF of energizing the PCV, which is controlled by the Engine ECM. The ON/OFF timing is controlled based on signals from various sensors to provide optimal rail pressure.
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| Illustration 6 | g03842520 |
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(1) Element
(2) Check ball (3) Spring (4) Holder (5) Plunger | |
The delivery valve location is shown in Illustration 6 and is composed of a check ball, spring, and holder.
When the pressure on the plunger side equals/exceeds the pressure on the rail side, the check ball opens and discharges fuel. As soon as the fuel pressure feed is complete, the check ball is pressed back by the spring, and when the check ball touches the seat of the element, cuts off the rail side from the plunger side, thus preventing any backflow of fuel.
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| Illustration 7 | g03842303 |
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(1) PCV (Pre-Stroke Control Valve)
(2) Housing (3) Camshaft (4) Delivery Valve (5) Plunger (6) Tappet (7) Feed Pump (8) Cam | |
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| Illustration 8 | g03842484 |
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(1) PCV (Pre-Stroke Control Valve)
(2) Housing (3) Camshaft (4) Delivery Valve (5) Plunger (7) Feed Pump (8) Cam (9) Plunger Chamber (A) Suction Stroke (B) Pre-Stroke (C) From Fuel Filter (D) To Fuel Return (E) Compression Start Stroke (F) Pressure Feed Stroke (G) To Fuel Rail Manifold | |
The pump unit works to increase the pressure of fuel received from the PCV and is composed of a camshaft (3), tappet (6), and plunger (5).
When the camshaft (3) rotates, the cam (8) rotates eccentrically and the tappet (6) is driven up and down by it, which operates the plunger (5) through their cycles.
- A: Suction Stroke- The PCV is opened when the plunger falls and fuel is suctioned into the plunger chamber via PCV.
- B: Pre-Stroke- Even after the plunger enters the raise process, fuel suctioned passes through the PCV, and is discharged without being pressurized while the PCV is not energized and the valve is open.
- E: Compression Start Stroke- The PCV is energized which closes off the passages from the fuel filter (C) and the fuel return (D). The cam rotation moves the plunger upward which increases the fuel pressure to the delivery valve (4).
- F: Pressure Feed Stroke- When the PCV is energized and the valve opened based on timing suitable for the amount of fuel needed, the return path is closed by the PCV and the fuel inside the plunger chamber is pressurized. This opens the delivery valve and fuel is fed into the rail.
The discharge amount is based on the lift distance of the plunger after the PCV valve closes.
Changing of the PCV valve close timing changes the amount discharged, thus controlling rail pressure.
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| Illustration 9 | g03858413 |
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(39) Pressure limiter
(40) Fuel rail (41) Pressure Discharge Valve | |
The rail stores fuel at the high pressure applied by the supply pump and supplies the shared pressure to the injectors of each cylinder. The rail incorporates a rail pressure sensor and a pressure limiter.
The pressure of the fuel in the rail is detected by the rail pressure sensor, and optimal feedback control is provided for the engine RPM and load. This greatly improves the ability to raise the pressure at low RPMs and enables high-pressure injection from low speed ranges.
The pressure discharge valve opens when the rail pressure exceeds
Fuel discharged by the pressure discharge valve returns to the fuel tank.
The rail pressure sensor is mounted on the rail, detects the pressure inside the rail and sends a signal to the engine ECM.
This sensor is a semi-conductor type of pressure sensor in which increasing the pressure on the silicon element changes the electrical resistance. Note that the rail pressure sensor is not treated as a part, so replacement requires replacing the rail assembly.
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| Illustration 10 | g02917396 |
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(42) Engine ECM
(43) Rail Pressure Sensor (44) Rail (45) Supply Pump (46) Two-way Valve (47) Discharge Orifice (48) Control Chamber (49) Command Piston (50) Needle Valve (51) Nozzle | |
The injectors inject high-pressure fuel from the rail into the combustion chamber of the engine, using signals from the engine ECM to produce the ideal timing, amount of fuel, mixture, and spray.
The injector injects a finely tuned spray in three pulses during the combustion stage. First a small amount is injected, mitigating the effect of the initial burn and reducing NOx (oxides of nitrogen) and noise. The main injection follows with the real burn. The last stage reducing particulate matter generated by the main injection.
Injectors consist of nozzle components (nozzle) and needle valve), a two-way valve, which controls the volume and mixture of fuel, a control chamber with an intake orifice and discharge orifice, a command piston and a nozzle spring.
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| Illustration 11 | g03858420 |
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(A) Injection Stop
(B) Injection Start (C) Injection Finish (D) To Fuel Tank (E) From Rail (48) Control Chamber (50) Needle Valve (52) Solenoid (53) Control Valve Spring (54) Control Valve (55) Nozzle Seat (56) Sub Discharge (57) Intermediate Chamber (58) Intake Orifice (59) Discharge Orifice (60) Control Plate (61) Control Plate Spring (62) high Pressure Circular Groove | |
The Engine ECM controls injection of the injectors by controlling the fuel pressure in the injector control chamber (59).
The system for controlling the pressure of the control chamber works by energizing the solenoid, which opens the passage of the chamber discharge orifice and the fuel is injected due to the drop in pressure. When the current stops, the pressure in the control chamber returns to what the pressure was and injection ceases.
With no current to the solenoid, the control valve cuts off the discharge orifice passage, so rail pressure is applied to the control chamber and the bottom of the needle valve. As the diameter of the command piston on the control chamber side is larger than the diameter of the bottom of the needle valve, the piston works to push the needle valve down, which is compounded by the nozzle spring pushing the needle valve down, and the needle valve is closed.
When the solenoid is energized, it draws up the control valve, opening the passage of the discharge orifice, returning fuel in the control chamber to the fuel tank via the leak passage and dropping the pressure.
The drop in the pressure of the control chamber causes the pressure applied to the bottom of the needle valve to become greater than the pressure on the control chamber side, and the needle valve compresses the nozzle spring and starts injecting fuel.
When current to the solenoid stops, the control valve lowers and the discharge orifice passage is closed. When the passage of the discharge orifice closes, the fuel pressure in the control chamber recovers to the rail pressure, so the needle valve is pressed back via the command piston, stopping the injection.
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| Illustration 12 | g03858294 |
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(63) Injector
(64) Rated Amperage Circuit (65) High-voltage Generating Circuit (66) Control Circuit (67) Engine ECM | |
To increase the responsiveness of the injector, the voltage that drives the injector is raised to a high voltage, accelerating the magnetization of the solenoid and increasing the responsiveness of the control valve.
The battery voltage is raised to about 110 V by a high-voltage generating circuit inside the ECM and that voltage is supplied to the injector to actuate it.
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| Illustration 13 | g02917767 |
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(65) QR Code
(66) ID Code | |
Injectors are processed to exacting tolerances, but there are minute variations in the amount they inject, so to correct for these variations, a correction volume is recorded on the QR/ID codes of the injectors.
During manufacture, the QR code is read by a scanner and the correction value is registered in the ECM.
Note: When replacing an injector, register the ID code if the replacement injector into the ECM. Refer to Troubleshooting, "Injector Trim File - Install - Injector Trim Code - Install" for more information.
Note: When replacing the engine ECM, register all of the ID codes for the injectors into the new ECM. Refer to Troubleshooting, "Injector Trim File - Install - Injector Trim Code - Install" for more information.