Operating principles
The ECU (MS6.3 or EDC 16) processes the data from the atmospheric pressure sensor, coolant sensor, engine rpm sensor, accelerator pedal potentiometer and controls the modulating solenoid valve via a PWM signal according to programmed settings.
The control signal output by the ECU controls the modulating solenoid valve which puts the brake booster vacuum circuit into communication with that of the EGR.
The vacuum created in the EGR circuit depends on the control signal.
The vacuum acts on the pneumatic EGR valve by recalling and lifting the shutter which normally closes the passage of exhaust gasses to suction.
This puts the exhaust manifold into communication with the suction manifold and part of the exhaust gasses flows into the intake manifold.
The control signal from the ECU to the modulating valve is cancelled during engine conditions not requiring exhaust gas recirculation (cranking, cold engine, idling, load request, high altitude). The solenoid valve closes the connection between the brake booster vacuum circuit and the EGR circuit; at the same time, atmospheric pressure is re-established in the EGR circuit by letting in air through the specific air cleaner.
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Figure 17
a. Brake booster vacuum circuit - b. EGR modulated vacuum circuit
1. ECU - 2. High pressure pump - 3. Coolant temperature sensor - 4. Engine rpm sensor - 5. EGR pneumatic valve - 6. Flow meter 7. Suction air cleaner 8. Modulating solenoid valve 9. Air cleaner 10. Vacuum brake booster 11. Reservoir
-12. Vacuum unit.
EGR system operation
The EGR system is similar to that fitted on 8140.63 engines and described in the specific system section.
Differences with respect to the previous version fitted on 8140.63 engines include: application of an exhaust gas heat exchanger and air flow meter, governing system implementing EDC MS6.3 or EDC 16, different modulating solenoid valve and pneumatic EGR calibration values.
EXHAUST GAS RECIRCULATION (EGR) SYSTEM (Illustration, if available)
Air flow meter
1. Connector - 2. Flow meter body - 3. Air and recirculated gas inlet mesh - 4. Suction air temperature
sensor 5. Power 6. Ground 7. Reference voltage -8. Output signal.
The heated film flow meter is arranged between the turbine and the intercooler.
The suction air temperature sensor is built into the flow meter; the flow meter is connected to the ECU pins A5/A17/A18/A26/A28.
Operation
The hot film membrane temperature is kept constant (approximately 120°C higher than suction air temperature) by a heating resistor.
The air mass crossing the duct tends to subtract heat from the membrane. Consequently more current is required through the resistor to keep the temperature constant.
Current uptake is proportional to the mass of air flowing into the engine. It is measured by a Wheatstone bridge and the resulting signal is sent to the ECU.
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EXHAUST GAS COOLING
A. Intake exhaust gas — B. Cooled exhaust gas — C. Coolant to heater — D. Gas from E.G.R. valve — E. Coolant arriving from cylinder head.
Gas from E.G.R.
SECTION 2 Fuel
Page
OPERATION. . . 3 HYDRAULIC SYSTEM. . . 5 - Fuel pump (if provided) . . . 5 - Specifications . . . 5 - Fuel filter . . . 6 - Fuel pipes . . . 6 - Tightening torques . . . 6 - High-pressure pump. . . 7 - High-pressure pump internal structure. . . 9 - Working principle. . . 10 - Pressure control valve . . . 13 MECHANICAL SUPPLY PUMP. . . 13 - Hydraulic accumulator (rail) . . . 14 - Overpressure valve
(for forged hydraulic accumulator) . . . 14 ELECTRO-INJECTORS . . . 14 - Operation . . . 15
OPERATION
In this injection system, the pressure regulator, located upstream from the high-pressure pump, governs the flow of fuel needed in the low-pressure system. Afterwards, the high-pressure pump correctly supplies the hydraulic accumulator.
This solution, pressurizing solely the necessary fuel, improves the energy efficiency and limits heating the fuel in the system. The relief valve fitted on the high-pressure pump has the function of keeping the pressure, at the pressure regulator inlet, constant at 5 bars; irrespective of the efficiency of the fuel filter and of the system upstream. The action of the relief valve causes an increase in the flow of fuel in the high-pressure pump cooling circuit.
The high-pressure pump continually keeps the fuel at the working pressure, irrespective of the timing and the cylinder that is to receive the injection and accumulates it in a duct common to all the electro-injectors.
At the electro-injector inlet, there is therefore always fuel at the injection pressure calculated by the electronic control unit.
When the solenoid valve of an electro-injector is energized by the electronic control unit, fuel taken straight from the hydraulic accumulator gets injected into the relevant cylinder.
The hydraulic system is made out of a low-pressure fuel recirculation circuit and a high-pressure circuit.
The high-pressure circuit is composed of the following pipes:
- pipe connecting the high-pressure pump outlet to the Rail;
- hydraulic accumulator;
- pipes supplying the electro-injectors.
The low-pressure circuit is composed of the following pipes:
- fuel intake pipe from the tank to the pre-filter;
- pipes supplying the mechanical supply pump and the pre-filter;
- pipes supplying the high-pressure pump via the fuel filter.
The fuel system is completed by the fuel outlet circuit from the hydraulic accumulator and from the electro-injectors.
According to the high performance of this hydraulic system, for reasons of safety it is necessary to:
- avoid connecting high-pressure pipe fittings with approximate tightening;
- avoid disconnecting the high-pressure pipes with the engine running (NEVER try bleeding, which is both pointless and dangerous).
The integrity of the low-pressure circuit is also essential for the system to work properly; it is therefore necessary to avoid all manipulation and modifications and act only in the event of leakage.
The pipes connected to the fuel filter mounting are quick-coupling ones.
Before fitting them, make sure the couplings and the associated fittings on the mounting are clean.
NOTE
Figure 1
FUEL RECIRCULATION AND SUPPLY SYSTEM DIAGRAM
1. CP3 high-pressure pump with integrated supply pump — 2. Fuel arrival pipe from the filter — 3. Pressure regulator — 4. Water in filter sensor — 5. Fuel filter with water separator — 6. Fuel temperature sensor — 7. Fuel warming — 8. Fuel delivery pipe to the filter — 9. Fuel return pipe to the tank — 10. Fuel check valve — 11. Multiple coupling — 12. Fuel return low pressure piping - 13. Welded version hydraulic accumulator - 14. High-pressure delivery pipe to the
hydraulic accumulator — 15. Low-pressure return pipe from the hydraulic accumulator to the multiple coupling — 16. Overpressure valve — 17. Forged version hydraulic accumulator — 18. Pressure sensor — 19. High-pressure pipe between
hydraulic accumulator and electro-injectors — 20. Electro-injectors — 21. Return pipe from the electro-injectors to the high-pressure pump CP3.
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high pressure low pressure
Figure 2
Specifications
Delivery pressure: 2.5 bar
Flow rate: > 155 litres/h
Power supply: 13.5 V - < 5 A
Coil resistance at 20°C: 28.5 Ohms
HYDRAULIC SYSTEM