41
FUEL INJECTION SYSTEM
FUEL INJECTION SYSTEM
This portion of the presentation describes the principles of operation of the HEUI Fuel Injection System as is used on the 3408E and 3412E engines.
INSTRUCTOR NOTE: The various color codes which will be used in this section of the presentation to identify flow and pressures are: Hydraulic and Lubrication Circuits
Red - High pressure oil
Red and White Stripes - Reduced pressure oil
Brown - Lube oil pressure
Green - Lube oil suction or return
Fuel Circuits
Red - High pressure fuel
Red and White Stripes - Fuel transfer pump pressure
42 PUMP CONTROL VALVE OIL FILTER OIL COOLER HEUI HEUI OIL SUMP HYDRAULIC PRESSURE SENSOR HYDRAULIC TEMPERATURE SENSOR COLD START OIL
RESERVOIR OIL PRESSURE SENSOR ECM HYDRAULIC SUPPLY PUMP GROUP COOL DOWN CIRCUIT FUEL TANK FUEL TEMPERATURE SENSOR PRESSURE REGULATING VALVE SECONDARY FUEL FILTER FUEL TRANSFER PUMP PRIMARY FUEL FILTER WATER SEPARATOR LUBE OIL PUMP TO LUBE SYSTEM
3408E/3412E HEUI FUEL SYSTEM
FLUID MANIFOLD HYDRAULIC PASSAGE
FLUID MANIFOLD HYDRAULIC PASSAGE
Actuation of the fuel injection system is accomplished using hydraulics, rather than the conventional camshaft actuation commonly found on other diesel fuel systems.
Hydraulic actuation offers several advantages compared to mechanical actuation, including the ability to make injection pressure independent of engine operating speed. This capability is especially advantageous in many respects, including transient engine response, cold starting, emissions and noise control.
INSTRUCTOR NOTE: The following schematics may appear identical in the black and white illustrations. However, the actual slides are colored differently.
• HEUI principle components: 1. Hydraulic supply pump group 2. ECM 3. Temperature sensor 4. Pressure sensor 5. Injector 43 1 2 3 5 4 System Components
To review, the 3400 HEUI hydraulic and fuel supply circuits contain the following major components:
• Hydraulic Supply Pump Group (1) including: - Hydraulic pump
- Fuel transfer pump - Pump control valve
• Electronic Control Module (ECM) (2) • Electronic Sensors (3 and 4)
- Hydraulic temperature - Hydraulic pressure • Injectors (5)
• Hydraulic supply pump group:
1. Hydraulic pump
2. Pump control valve
3. Transfer pump
44
1
2
3
The following components are integrated into a single unit called the Hydraulic Supply Pump Group:
- Hydraulic pump (1) - Pump control valve (2) - Transfer pump (3)
This pump group is located in the vee of the engine and is in the same position as the fuel injection pump on earlier engines.
Three fluid circuits are included in the system: low pressure oil, high pressure oil (hydraulic), and low pressure fuel supply.
NOTE TO THE INSTRUCTOR: These components and circuits will be covered in detail later in the presentation.
45
• Low pressure oil supply
• Cold start reservoir
• Pressure sensor • Temperature sensor TO LUBE SYSTEM FUEL TRANSFER PUMP PUMP CONTROL VALVE OIL FILTER
3408E/3412E HEUI FUEL SYSTEM
OIL COOLER HEUI HEUI OIL SUMP HYDRAULIC PRESSURE SENSOR HYDRAULIC TEMPERATURE SENSOR OIL PRESSURE SENSOR ECM COOL DOWN CIRCUIT LOW PRESSURE OIL (HYDRAULIC) SUPPLY
FUEL TANK FUEL TEMPERATURE SENSOR PRESSURE REGULATING VALVE SECONDARY FUEL FILTER PRIMARY FUEL FILTER WATER SEPARATOR LUBE OIL PUMP COLD START OIL RESERVOIR HYDRAULIC SUPPLY PUMP GROUP FLUID MANIFOLD HYDRAULIC PASSAGE FLUID MANIFOLD HYDRAULIC PASSAGE System Operation
On a HEUI equipped engine, the lubrication pump has two functions: 1. Provides lubrication to the engine
2. Provides low pressure charge oil to the HEUI hydraulic pump The engine lubrication pump has been enlarged to provide the required increase in flow.
The hydraulic pump has a Cold Start Oil Reservoir. This reservoir prevents the hydraulic pump from cavitating during initial engine
cranking until the lubrication pump can supply adequate charge pressure. An oil pressure sensor is located in the Cold Start Oil Reservoir, which is the inlet to the hydraulic oil pump. The sensor monitors lubrication oil pressure. An oil temperature sensor is also installed in the reservoir. This sensor will be referred to as the "hydraulic temperature sensor" as it is used for this purpose.
46 • High pressure actuates hydraulics TO LUBE SYSTEM FUEL TRANSFER PUMP PUMP CONTROL VALVE OIL FILTER
3408E/3412E HEUI FUEL SYSTEM
OIL COOLER HEUI HEUI OIL SUMP HYDRAULIC PRESSURE SENSOR HYDRAULIC TEMPERATURE SENSOR OIL PRESSURE SENSOR HYDRAULIC SUPPLY PUMP GROUP COOL DOWN CIRCUIT HIGH PRESSURE HYDRAULICS
FUEL TEMPERATURE SENSOR ECM FUEL TANK PRESSURE REGULATING VALVE SECONDARY FUEL FILTER PRIMARY FUEL FILTER WATER SEPARATOR LUBE OIL PUMP COLD START OIL RESERVOIR FLUID MANIFOLD HYDRAULIC PASSAGE FLUID MANIFOLD HYDRAULIC PASSAGE
During normal operation conditions, oil is pressurized between
5000 and 21500 kPa (725 and 3100 psi) by the high pressure hydraulic pump to actuate the injectors. The level of hydraulic pressure is
controlled by the ECM, which signals the pump control valve to upstroke the hydraulic pump.
When the engine is running, high pressure oil is available to all injectors at all times.
Oil from the high pressure pump enters the two oil supply passages. Reverse flow check valves are used to prevent pressure surges between the oil passages on opposite banks. The oil supply passages are connected hydraulically to the injectors by jumper tubes. Oil used by the injectors is released below the valve covers and drains back to the sump through the pushrod compartments.
47
• Low pressure fuel supply • Injector cooling TO LUBE SYSTEM FUEL TRANSFER PUMP PRESSURE REGULATING VALVE PUMP CONTROL VALVE OIL FILTER
3408E/3412E HEUI FUEL SYSTEM
OIL COOLER LUBE OIL PUMP HEUI HEUI OIL SUMP HYDRAULIC PRESSURE SENSOR HYDRAULIC TEMPERATURE SENSOR OIL PRESSURE SENSOR ECM COOL DOWN CIRCUIT LOW PRESSURE FUEL SUPPLY
FUEL TEMPERATURE SENSOR FUEL TANK SECONDARY FUEL FILTER (2 MICRON) PRIMARY FUEL FILTER WATER SEPARATOR COLD START OIL RESERVOIR HYDRAULIC SUPPLY PUMP GROUP FLUID MANIFOLD HYDRAULIC PASSAGE FLUID MANIFOLD HYDRAULIC PASSAGE
Fuel is drawn from the tank through the water separator and the hand priming pump by a gear-type transfer pump. The fuel is then directed through the Electronic Control Module (ECM) housing for cooling purposes. The fuel then flows through the secondary fuel filter.
Next, the fuel enters the low pressure supply gallery located in the fluid supply manifolds on top of the cylinder heads. Any excess fuel not injected leaves the manifold. The flow is then combined into one line and passes through the pressure regulating valve, which is set between
310 and 415 kPa (45 and 60 psi). From the pressure regulating valve, the excess flow returns to the tank. The ratio of fuel between combustion and fuel returned to the tank is about 1:3 (i.e. four times the volume required for combustion is supplied to the system for combustion and injector cooling purposes).
A fuel temperature sensor is installed in the fuel supply system to compensate for power losses caused by varying fuel temperatures.
48
• Fuel and oil flow LOW PRESSURE FUEL SUPPLY CYLINDER HEAD INJECTOR SLEEVE FLUID SUPPLY MANIFOLD INJECTOR INJECTOR OIL ADAPTER JUMPER TUBE INJECTOR CLAMP HIGH PRESSURE HYDRAULIC PASSAGE CYLINDER HEAD ROCKER ARM BASE LUBE OIL PASSAGE
CYLINDER BLOCK COOLANT
METAL WASHER
INJECTOR FLUID FLOW HIGH PRESSURE HYDRAULIC OIL
Hydraulic Unit Injector Operation
High pressure hydraulic oil is provided to each injector from the hydraulic supply passages through individual jumper tubes.
Fuel is supplied to the injector by the low pressure supply passage located in the fluid manifolds (described on the next slide).
Special "Viton" o-rings are used in the hydraulic joints between the injector and the fluid manifold.
NOTE: This slide and the following slide depart from the color legend by using orange for high pressure oil to avoid confusion between the two fluids.
49
• Low pressure fuel supply to injector FLUID SUPPLY MANIFOLD INJECTOR CYLINDER HEAD LOWER INJECTOR O-RING SEAL UPPER INJECTOR O-RING SEAL
INJECTOR FUEL SUPPLY
METAL-TO- METAL CONTACT LOW PRESSURE FUEL SUPPLY CYLINDER HEAD INJECTOR SLEEVE UPPER SLEEVE O-RING SEAL LOWER SLEEVE O-RING SEAL
Low pressure fuel is supplied to the inlet of the injector through a drilled passage located in each Fluid Supply Manifold.
The fuel supply to each injector is sealed from the combustion chamber and the area below the valve cover by upper and lower o-ring seals between the injector and the cylinder head injector sleeve.
Combustion chamber gases are prevented from entering the fuel supply passage by a metal-to-metal contact between the cylinder head injector sleeve and the injector.
The cylinder head injector sleeve is threaded into the cylinder head. A metal washer is used to seal the lower end of the adapter to prevent leakage between the cooling system and the combustion chamber.
• Fluid supply manifold • Supply passages: 1. Hydraulic 2. Lubrication 3. Fuel 50 2 1 3
The following passages are located in the Fluid Supply Manifold: - Hydraulic supply passage (1)
- Lubrication supply passage (2) - Fuel supply passage (3)
The fluid supply manifold is mounted on the cylinder head and carries injector actuation hydraulic oil under pressure through the jumper tubes to the injectors.
Low pressure fuel and lubrication oil to the valve mechanism are also directed through the manifold. These passages are shown in the sectional view on the next slide.
51
• Supply passages
• Additional fuel for cooling
• Fuel seals
LOW PRESSURE FUEL SUPPLY PASSAGE
CYLINDER HEAD INJECTOR SLEEVE HIGH PRESSURE HYDRAULIC PASSAGE ROCKER ARM BASE LUBRICATION OIL PASSAGE EXTRACTOR SPLINES FUEL SEALS
FLUID SUPPLY MANIFOLD
This sectional view shows the various passages in the Fluid Supply Manifold.
- High pressure hydraulic supply passages - Low pressure fuel supply passages - Lubrication oil supply passages
The fuel enters the front of the manifold and exits the rear. Cooling of the injectors is achieved by circulating a larger volume of fuel past the
injectors than is required for combustion.
Initially, fuel circulates around the outside of the injector sleeve and is contained between the sleeve and the fluid supply manifold by the upper and lower injector sleeve fuel seals.
• Jumper tube and oil adaptor
52
1
2
The Jumper Tube (1) and Injector Oil Adaptor (2) direct hydraulic oil from the fluid manifold high pressure passage to the injector.
A specific procedure to tighten the six bolts (for the Jumper Tube and Adaptor) must be followed when installing the jumper tube. This procedure follows later in the presentation.
NOTICE
Failure to follow the correct tightening procedure can result in low power complaints caused by internal hydraulic leaks. Also, internal strains on the injector caused by an improper tightening procedure can cause changes in internal injector clearances which can decrease performance and injector life.
53
• Injector current waveform
• Two current levels
INJECTION CURRENT WAVEFORM
0
1
2
3
4
CURRENT FLOW
TIME (MILLISECONDS) PULL-IN PEAK CURRENT
HOLD-IN PEAK CURRENT ONE CYCLE
5
Injector Operation Characteristics
The quantity of fuel delivered is controlled by varying the time the
solenoid is energized. This period of time, called "duration," is calculated by the ECM to ensure delivery of the correct amount of fuel. Other inputs affect calculation of on-time, including (but not limited to) hydraulic supply pressure, oil temperature and mapped injector performance characteristics. Two current levels are generated in the wave form:
1. Pull-in current is higher to create a stronger magnetic field to attract the armature and lift the injector poppet valve off its seat against spring force.
2. Hold-in current is used to hold the armature and poppet off its seat. Lower current reduces heat in the solenoid and increases solenoid life.
The injector performance map shows delivery as a function of on-time, pump pressure, and oil temperature, and is stored in the ECM memory.
54
• Waveform and injector response
WAVEFORM AND RESPONSE CHARACTERISTICS
0
1
2
3
4
CURRENT FLOW TIME (MILLISECONDS) CURRENT POPPET LIFT INJECTION RATE START OF INJECTION DURATION5
END OF INJECTIONThis slide shows that, as the ECM energizes the solenoid, the poppet valve movement follows. Then, the injector rate increases for the start of
injection. The end of injection occurs as the rate drops toward zero. Therefore:
• Engine fuel timing is a function of the start of injection. • Fuel quantity is a function of:
- The duration of injection
- Injection actuation (hydraulic) pressure
• Pull-in current • Poppet lift - Blue line • Start of injection - Purple line • Injection rate - Purple line • End of injection
The ECM sends a higher current to the solenoid to create a strong
magnetic field. This strong field is needed to create maximum pull on the armature, which is at its farthest distance from the solenoid.
The poppet is normally held on its inlet seat by the poppet spring. The higher pull-in current attracts the armature and lifts the poppet off its inlet seat and toward the exhaust seat against the spring force. The ECM reduces the current level to hold-in current and the poppet is held on its exhaust seat.
Injection starts after the exhaust seat closes and oil pressure pushes the intensifier piston and plunger down. The downward movement of the plunger pressurizes the fuel to approximately 31000 kPa (4500 psi) and the check valve lifts, allowing fuel to enter the cylinder. The time at which fuel leaves the tip is called the "start of injection."
The rate at which fuel is injected is controlled by injection hydraulic pressure. Higher hydraulic pressure pushes the piston and plunger faster, causing a higher flow rate through the nozzle tip.
When the ECM ends injection, it terminates the hold-in current which causes the magnetic field in the solenoid to collapse. The poppet spring then moves the poppet back to the inlet seat. As the poppet travels back to the inlet seat, hydraulic oil is shut off, and the downward travel of the piston and plunger reverses, filling the barrel for the next injection sequence.
As pressure drops below the plunger and nozzle areas, the valve closing pressure, which is about 21000 kPa (3000 psi), causes this pressure to be retained in the nozzle for the next cycle.
INSTRUCTOR NOTE: If a disassembled or a cutaway injector is available, it is recommended that the preceding sequence be reviewed using the actual components.
• Major components
• Seals
55
Injector Components
The 3408E/3412E unit injector has been designed to represent the state of the art in the industry. This section of the presentation will describe all the components and their functions.
This slide shows a cutaway injector and the injector sleeve. Note the following major injector component groups:
- Valve body group with solenoid and poppet valve - Barrel group with intensifier piston and plunger - Nozzle group
The injector sleeve has four seal grooves. The two upper grooves have the seals which contain the fuel within the fluid manifold (shown in more detail later).
The two lower seals contain the coolant below the cylinder upper deck. A metal washer seals the lower part of the sleeve and prevents coolant from entering the combustion chamber.
56
• Three main groups
HEUI UNIT INJECTOR 3 MAIN GROUPS
VALVE BODY GROUP
BARREL GROUP
NOZZLE GROUP
The injector consists of three basic groups which will be described in detail:
- Valve Body Group - Barrel Group - Nozzle Group
This view and those that follow show the exhaust port on the injector venting the return oil downward. This condition is a modification from the previous design which vented the oil upward. These injectors are interchangeable. However, the newer injector reduces the tendency of the engine to discharge oil mist from the breather.
57
• Injector components
STOP PIN PLUNGER SPRING SEAL BARREL BALL
DOWEL SEAL INTENSIFIER PISTON RETAINER RING WASHER STOP PLATE CHECK PLATE BALL STOP DOWEL SPRING LIFT SPACER SLEEVE DOWEL CHECK TIP CASE POPPET SPRING SLEEVE SHIM SEAL
ADAPTER BOLT SPACER ARMATURE SCREW SOLENOID ASSEMBLY SCREW BODY VALVE BODY GROUP
BARREL GROUP
NOZZLE GROUP
3408E/3412E HEUI INJECTOR
COMPONENTS
The HEUI injector was designed with a minimum of component parts. The injector contains 35 part numbers.
This exploded view shows all the components by assemblies as follows: The Valve Body Group contains the solenoid, armature and the poppet valve. This assembly directs the oil to the hydraulic intensifier piston which moves the fuel plunger.
The Barrel Group contains the high pressure fuel plunger. The Nozzle Group contains the case, tip, check valve and nozzle.
NOTE: Although the injector components are explained in this presentation, it should be noted that no individual parts of the injector are serviced. This injector is precision assembled by a machine, and replacing individual injector components would result in unacceptable performance problems or injector failures.
58 • Injector component parts SHIM BARREL PISTON VALVE FUEL INLET CHECK VALVE PIN SPACER ADAPTER SPACER ARMATURE SOLENOID WASHER PLUNGER SLEEVE SLEEVE UNIT INJECTOR COMPONENTS
LOWER FUEL SEAL VALVE BODY
UPPER FUEL SEAL
NOZZLE CHECK
This slide shows the component parts in the three basic groups discussed previously.
The valve body has three parts (body, adaptor and spacer) which are assembled with great precision. Any damage sustained in the valve body area during installation or removal will cause an injector failure.
NOTICE
The correct injector removal procedures and tooling specified in the service manual must always be used. Any leverage applied below the valve body can cause deformation of the poppet valve bore and possible injector failure.
59 HORIZONTAL BOLTS JUMPER TUBE INJECTOR CLAMP VERTICAL BOLTS
INJECTOR INSTALLATION
ALLEN SCREWS INJECTOR OIL ADAPTORInjector Removal and Installation
The correct procedures for injector removal and installation must be followed to avoid strain on the injector and hydraulic leaks in the jumper tube area. The three mating surfaces of the jumper tube, oil adaptor and injector must be aligned before final torque is applied.
INSTRUCTOR NOTE : At this time, it is recommended that the injector removal and installation procedures be demonstrated. Emphasis should be placed on the use of the correct puller during removal (rather than a pry bar, which could result in injector damage). Also, disassemble a used injector to identify the various components shown on this slide.
• Injector assembly and installation
This portion of the assembly procedure ensures that all mating and sealing faces are flush and in complete contact before tightening the bolts.
1. Clean the faces of the injector and the injector sleeve and install new o-rings.
2. Lubricate the o-rings with oil and insert the injector in the injector sleeve.
3. Visually align the injector with the flat surface parallel to the centerline of the engine.
4. Position the injector clamp on the injector and tighten the bolt to 47 ± 9 N•m (35 ± 7 lb. ft.).
5. Install new seals on the jumper tube and rocker arm base. 6. Place the injector oil adaptor and jumper tube in position. 7. Install the allen screws and hex head bolts finger tight. If the
injector oil adaptor was previously installed on the injector, loosen the allen screws.
The objective at this point in the procedure is to bring all the mating faces into complete contact and alignment before starting the final torque procedure.
Failure to align the components will put a strain on the injector which will then distort the poppet valve and barrel bores. These components operate with a clearance of 5 microns because of the high injection and hydraulic pressures. Therefore, even a small amount of distortion will cause a seizure.
Additionally, some misalignment could cause combustion gases to enter the supply system.
• Injector installation torque sequence
After all the mating surfaces are aligned, the torquing procedure can be performed:
1. Tighten the allen screws and hex head bolts finger tight or just sufficiently to bring the mating surfaces together and into alignment.
2. Apply an initial torque to the vertical hex head bolts of 5 ± 3 N•m (4 ± 2 lb. ft.).
3. Apply an initial torque to the horizontal hex head bolts of 5 ± 3 N•m (4 ± 2 lb. ft.).
4. Apply an initial torque to the allen screws of 1 ± 0.2 N•m (10 ± 2 lb. in.).
5. Final torque the vertical hex head bolts to 47 ± 9 N•m (35 ± 7 lb. ft.).
6. Final torque the horizontal hex head bolts to 47 ± 9 N•m (35 ± 7 lb. ft.).
7. Final torque the allen screws to 12 ± 3 N•m (9 ± 2 lb. ft.).
8. Check the system for leaks (crank with injection disabled). Then, check the hydraulic pressure (compare with desired pressure).
A number of possibilities for leaks can exist. Oil under high pressure may leak from the jumper tube joints or from the injector valve body exhaust port. Fuel could leak from the upper seal on the injector. Also,
combustion gas can possibly leak from the base of the injector.
If air has entered the fuel supply system, multiple injectors on one bank may malfunction. If the above procedure was not followed, air could enter past the lower o-ring seal. If this condition occurs, remove the injector and check for carbon below the lower o-ring seal. Replace the seal and perform the torque sequence.
Air in the system may be detected by lightly touching the flexible return line and checking for extreme pulsations or pressure spikes felt through the line. As an alternative, install a sight glass in each return line, run the engine and check for air.
Combustion gas leakage will usually affect the injector with the leak followed by the injectors downstream (toward the rear) of the leak. In conclusion, the system is reliable. However, failure to follow these procedures may cause malfunctions.
60
• Solenoid de-energized
• Solenoid energized
• Oil flows to intensifier piston
SOLENOID DE-ENERGIZED SOLENOID ENERGIZED
POPPET VALVE CLOSED POPPET VALVE OPEN
ARMATURE SCREW POPPET SPRING INLET VALVE SEAT SOLENOID POPPET VALVE ARMATURE EXHAUST VALVE SEAT
VALVE BODY GROUP
Injection Sequence
When the solenoid is de-energized, the poppet valve is held on its inlet (left) seat by the poppet spring. The poppet valve is connected to the armature by the armature screw. When the poppet is closed, the inlet seat prevents high pressure oil from entering the injector. The exhaust poppet seat is open, connecting the intensifier piston cavity to the atmosphere. Based on input signals from the various electronic sensors, the ECM calculates the quantity and timing of fuel to be delivered by the injector to the combustion chamber. At the appropriate time, the ECM sends an electrical current to the injector solenoid.
The solenoid develops a magnetic force which attracts the armature and shifts the poppet valve. The poppet valve moves against the spring force, opens the inlet seat and closes the exhaust (right) seat. Hydraulic pressure oil from the supply manifold is directed through the jumper tube to the top of the intensifier piston.
61
• Plunger moves down • Pressurizes fuel below
plunger • Pressure intensification FUEL INLET CHECK VALVE INTENSIFIER PISTON PLUNGER FUEL TO NOZZLE BARREL BARREL GROUP FUEL PRESSURE INCREASE
REVERSE FLOW CHECK VALVE
FUEL FROM TRANSFER PUMP
SUPPLY OIL
Supply oil flow from the poppet valve causes the intensifier piston and the fuel plunger to move downward. The displacement of the plunger
pressurizes the fuel trapped between the plunger face and the nozzle check seat.
NOTE: The intensifier piston has almost seven times the area of the fuel plunger. When the hydraulic circuit is supplying a pressure of 21000 kPa (3000 psi), approximately 145000 kPa (21000 psi) will be generated below the fuel plunger.
62
• Fuel atomization
VIEW OF STOP PLATE & REVERSE FLOW CHECK VALVE
REVERSE FLOW CHECK VALVE FUEL ATOMIZATION
NOZZLE GROUP
CHECK VALVEWhen the trapped pressure exceeds the nozzle valve opening pressure (VOP), typically 31000 kPa (4500 psi), the check valve lifts, and fuel flows through the holes in the nozzle into the combustion chamber. At the end of injection, the nozzle check valve closes at approximately
21000 kPa (3000 psi).
The reverse flow check valve is used to prevent combustion induced gas flow from entering the nozzle area.
The nozzle of the injector is very similar to the EUI unit injector. Six orifices, each with a diameter of 0.252 mm (.010 in.), are arranged at an angle of 140 degrees.
63
• End of injection
• Solenoid de-energized
• Poppet valve closes
INLET VALVE SEAT SOLENOID POPPET VALVE ARMATURE EXHAUST VALVE SEAT
SOLENOID DE-ENERGIZED
VALVE BODY GROUP
The end of injection is accomplished by shutting off the current from the ECM to the injector solenoid. The resulting loss of magnetic force on the armature allows the return spring force to shift the poppet valve off the exhaust seat.
The poppet returns to the inlet seat in the valve body, blocks the flow from the hydraulic oil supply, and simultaneously fully opens the exhaust valve seat. This action vents the injector internal hydraulic circuit below the valve cover.
64
• End of injection • Intensifier piston
moves up
• Nozzle check valve closes SHIM BARREL PISTON VALVE BALL PIN SPACER ADAPTER SPACER ARMATURE SOLENOID WASHER PLUNGER SLEEVE SLEEVE NOZZLE BODY UNIT INJECTOR END OF INJECTION CHECK
When vented, the intensifier piston and fuel plunger are pushed upward by the plunger return spring force until the intensifier piston contacts the valve body. This upward displacement of the intensifier piston vents spent oil from the injector below the valve cover.
Retraction of the fuel plunger decreases the pressure in the fuel chamber below the plunger, which permits the nozzle check valve to close when the pressure in the nozzle drops below the valve closing pressure (VCP) of approximately 21000 kPa (3000 psi).
65
• Barrel refilling
BARREL GROUP
REFILLING THE BARREL
BARREL PISTON FUEL INLET CHECK VALVE PIN SPACER WASHER PLUNGER SLEEVE NOZZLE NOZZLE CHECK VALVE FUEL EDGE FILTER
As the plunger continues to retract, the pressure below the plunger decreases below the fuel supply gallery pressure. The fuel inlet check valve then opens, allowing fuel to pass through the edge filter (next slide) to the supply gallery to refill the injector for the next injection sequence.
66
• Fuel edge filter
REVERSE FLOW CHECK VALVE
EDGE FILTER
EDGE FILTER FUEL INLET CHECK VALVE FUEL INLET FUEL INLETNote the location of the fuel edge filter. The edge filter is formed by two flat parallel surfaces that are approximately 130 microns apart. These surfaces trap and break down particles which might be big enough to plug the nozzle orifices.
67
• Injection rate shaping
• Low emission levels
• PRIME
PRIME INJECTION RATE SHAPING
0
1
2
3
4
TIME (MILLISECONDS)
5
PRIME = PRE-INJECTION METERING INJECTION RATE
DURATION START OF INJECTION
Another feature used in the injector for 3408E/3412E applications is an injection rate shaping device. Rate shaping refers to tailoring the way fuel is delivered to the engine to obtain a desirable result. In the 3408E/3412E application, rate shaping reduces the quantity of fuel delivered to the combustion chamber during the ignition delay period (i.e. the time between the start of injection and start of combustion) to levels which produce low engine combustion noise and low emissions.
The device used to create rate shaping is known as PRIME, an abbreviation for PRe-Injection MEtering. This device is basically a controlled spill port which serves to limit the amount of fuel delivered to the combustion chamber during the initial 25% displacement of the fuel plunger. This metering action produces the desired reduction of fuel delivery during the ignition delay period.
68
• Injection rate shaping
1. Start of injection 2. Pressure drop 3. Final increase • Benefits CROSS SECTION OF PLUNGER PRIME RATE SHAPING PASSAGE PLUNGER BARREL SPILL PORT FUEL TO NOZZLE GROUP
START OF INJECTION PRESSURE DROP
FINAL
PRESSURE INCREASE
BARREL GROUP
PRIME RATE SHAPING
OIL FLOW
This slide shows the three stages in PRIME rate shaping. 1. Injection pressure starts to increase and causes the initial
movement of the plunger.
2. When the prime rate shaping passage on the plunger is passing the spill port in the barrel, pressure decreases below VCP as
pressurized fuel leaks through the passage in the plunger into the spill port. At this time, nozzle flow momentarily decreases. 3. As the plunger continues downward, the PRIME rate passage passes the spill port and pressure will again increase, causing injection to resume.
This feature reduces emissions, smoke and noise. It also provides a
69
• Internal leakage
• Fluids are vented to pump inlet
BARREL GROUP
VENTING INTERNAL LEAKS
INTENSIFIER PISTON SEAL VENTING CHECK VALVE BARREL INTENSIFIER PISTON
During the normal injection cycle, the pressure of the oil supplied to the top of the intensifier piston can increase to 22800 kPa (3300 psi). A seal is installed to minimize leakage past the piston.
Some oil which is necessary for lubrication of the intensifier piston may pass the seal and settle momentarily below the piston.
Also, a small amount of fuel may leak past the plunger and barrel. This fuel will settle momentarily in the cavity below the intensifier piston. If the fluids which accumulate below the piston are not vented, a
hydraulic lock could occur. As the piston moves down, the fuel is ejected past the barrel ball check valve to the low pressure inlet. The check valve then closes during the plunger and piston upstroke.
70
• Injector check valves:
- Fuel inlet
- Barrel
- Reverse flow
- Nozzle
BARREL GROUP NOZZLE GROUP
FUEL INLET CHECK VALVE NOZZLE CHECK VALVE FUEL ATOMIZATION VENTING CHECK VALVE REVERSE FLOW CHECK VALVE
INJECTOR CHECK VALVES
Four check valves are installed in the injector. Three check valves are installed in the Barrel Group and one is installed in the Nozzle Group. The Fuel Inlet Check Valve allows fuel to fill the barrel below the plunger, but closes as the plunger moves down and pressure increases.
The Venting Check Valve vents fluids from below the intensifier piston. The Reverse Flow Check Valve prevents combustion gasses from flowing back through the injector from the nozzle.
The Nozzle Check Valve controls valve opening pressure by preventing the flow of fuel through the nozzle holes until sufficient pressure is available to lift the valve from its seat.
71
• Hydraulic pressure control
IDLE PEAK TORQUE RATED
INJECTION PRESSURE
MECHANICALLY ACTUATED FUEL SYSTEM
HEUI
ENGINE SPEED
HYDRAULIC INJECTION PRESSURE CONTROL
HYDRAULIC SYSTEM
The desired hydraulic actuation pressure for fuel injection can be controlled independent of engine speed.
Many combinations of on-time and hydraulic operating pressure exist which can result in a specific quantity of fuel per injector stroke being delivered to the combustion chamber. This characteristic is useful when tuning the engine to optimize performance, response, emissions, and other parameters.
This feature makes the HEUI system superior; injection pressure can reach its maximum value regardless of engine speed. Maximum injection pressure is normally required at full torque speed. This characteristic contrasts with pump and line systems where pressure is proportional to engine speed.
• Variable displacement piston pump
• Cold start oil reservoir
• Serviceable parts
72
Hydraulic Supply Pump Group
The 3408E/3412E Hydraulic Supply Pump Group is a variable
displacement, axial piston pump similar to those used in many machine hydraulic systems.
The pump features a nine piston rotating group and variable displacement control. The pump is driven by the engine timing gears at 1.167 times engine speed and produces 59 L/min. (15.5 gpm) at rated engine speed. Low pressure oil from the engine lubricating pump is supplied to the inlet of the pump Cold Start Oil Reservoir. The purpose of the reservoir is to keep the system primed during cool down. During cold starting
conditions, this volume of oil helps to shorten start times.
The lubrication system oil pressure and hydraulic temperature sensors are located in the reservoir.
The Hydraulic Supply Pump Group contains the following serviceable parts:
- Transfer Pump
- Reverse Flow Check Valves - Pump Control Valve
• Hydraulic supply pump mounting adapter
1. Pump drive splines 2. Alignment bolt hole 3. Atmospheric pressure sensor location 73 2 3 1
The Hydraulic Supply Pump group is mounted on the adapter shown on the slide. The pump drive shaft engages in the drive splines (1).
A large bolt is installed in the hole (2) in the adaptor base to provide good alignment between the adaptor and the engine block.
Note the location of the Atmospheric Pressure Sensor (3) in the housing. The Atmospheric Pressure sensor is vented to the atmosphere below the housing. The housing contains a foam plug to prevent the entry of dirt into the sensor.
74
• Pump priming
• Priming port
• Case drain orifice
• Priming procedure PRIMING PORT ORIFICE RESERVOIR SWASHPLATE TRANSFER PUMP COMPENSATOR VALVE
HEUI PUMP
VALVE BASE DRAIN PASSAGEPriming the pump after replacement is extremely important to prevent slipper pad overheating. Pump failure or damage will occur due to lack of lubrication if the case is not filled during replacement.
The priming port is located adjacent to the inlet tube (not shown) and is the rearmost of the two plugs. The front plug is the case drain passage and is vented over the pump drive gears. Therefore, the front plug cannot be used for priming.
A .50 mm (.020 in.) orifice is located between the fill port line and the case drain line. This orifice allows a continuous flow from the case to the drain circuit for lubrication, cooling and venting of air from the reservoir. The procedure to prime the Hydraulic Supply Pump case is:
1. Remove the plug from the priming port.
2. Fill the compartment with oil and replace the plug.
3. Fill the reservoir with oil (if the machine is not equipped with pre-lube).
• Fuel transfer pump (arrow)
75
The fuel transfer pump (arrow) is driven by a coupling that connects the end of the high pressure supply pump drive shaft to the transfer pump input shaft.
This gear pump has an integral relief valve set to open at 620 to 760 kPa (90 to 110 psi). This valve does not normally operate because the pressure regulating valve (next slide) is controlling the pressure. Fuel is drawn from the tank to the combined primary fuel filter/water separator. The fuel then passes through the ECM and the secondary fuel filter to the fluid manifold and the injectors.
• Pressure regulating valve
• Fuel pressure test plug (arrow)
76
Fuel system pressure is controlled by the Pressure Regulating Valve. This valve regulates pressure between 310 to 415 kPa (45 to 60 psi).
The valve is located downstream of the fluid manifold fuel passages and the injectors. Fuel which passes through the valve is returned to the fuel tank.
The fuel lines from both fuel passages in the manifolds are joined at the regulating valve.
Fuel pressure can be checked by removing the plug (arrow) and connecting a gauge.
77
• Cold start oil reservoir
• Reverse flow check valves TO LUBE SYSTEM FUEL TRANSFER PUMP PUMP CONTROL VALVE OIL FILTER OIL COOLER HEUI HEUI OIL SUMP HYDRAULIC PRESSURE SENSOR HYDRAULIC TEMPERATURE SENSOR OIL PRESSURE SENSOR ECM COOL DOWN CIRCUIT
COOL DOWN BYPASS CIRCUIT
FUEL TANK FUEL TEMPERATURE SENSOR PRESSURE REGULATING VALVE SECONDARY FUEL FILTER LUBE OIL PUMP PRIMARY FUEL FILTER WATER SEPARATOR FLUID MANIFOLD HYDRAULIC PASSAGE HYDRAULIC SUPPLY PUMP GROUP COLD START OIL RESERVOIR FLUID MANIFOLD HYDRAULIC PASSAGE DRAIN .020 IN. ORIFICE
The Cold Start Oil Reservoir is located above the Hydraulic Supply Pump Group. The Hydraulic (Oil) Temperature and Lube Oil Pressure Sensors are located at the top of the reservoir.
When the engine is shut down and oil in the supply manifolds cools and contracts, oil from the reservoir flows through the cool down circuit to the manifolds. This design prevents the formation of air bubbles in the hydraulic supply manifolds during cooling to provide fast starting and smooth running. A 0.50 mm (.020 in.) drilled passage in the reservoir allows the air to be vented through the case drain after start-up.
The Reverse Flow Check Valves prevent hydraulic surges between the oil supply passages and are used to maintain stable pressures. The valves are shown on the next slide.
• Reverse flow check valves (arrows)
78
This view shows the rear of the hydraulic supply pump with the aftercooler removed from the engine.
The Reverse Flow Check Valves (arrows) are located at the rear of the pump group to the right of the transfer pump. The high pressure lines to the manifolds are connected to the check valves.
79
• Reverse flow check valve
• Check valves block pressure surges from injectors
CHECK
FITTING VALVE BLOCK SPRING SEAT
REVERSE FLOW CHECK VALVE
FROM PUMP TO INJECTORS SEAT (END VIEW)
The hydraulic supply pump group has two outlet ports, each connected by steel tubes to a hydraulic supply manifold. An integral reverse flow check valve is located in each outlet port.
This view shows that pressure surges travelling back from the injectors toward the pump will cause the check valve to close and block any interference between the banks. In normal operation, the valve will oscillate at high frequency as it blocks the pressure surges.
The valve check fits loosely on the shaft to allow oil flow from the reservoir during the cooling process.
If the check valves were not in the system, pressure surges between the banks would cause erratic operation of the injectors by adversely affecting timing. The pressure surge causes the poppet valves to open prematurely. This condition would start
• Pump components:
1. Cold start reservoir
2. Swashplate 3. Swashplate pivot 4. Displacement control piston 5. Pump piston 6. Check valves 80 6 5 4 2 3 1
This cutaway view of the Hydraulic Supply Pump Group shows the following components:
Cold Start Oil Reservoir (1) Swashplate (2)
Swashplate Pivot (3)
Displacement Control Piston (4) Pump Pistons (5, one of seven shown) Check Valves (6)
• Valve components: 1. Compensator valve assembly 2. Pressure limiter spool 3. Load sensing spool 4. Check valve 5. Valve base • Oil passages:
6. Oil supply from pump
7. Pressure limiter to case drain
8. To displacement control piston 9. Pump control valve
to case drain • Pump components:
10. Transfer pump drive and mounting 11. Pump control valve
81 2 10 9 1 4 6 11 3 7 8 5
This cutaway view shows the compensator valve assembly and the pump control valve. Note the following components which will be referred to in the presentation:
Compensator Valve Assembly (1) Pressure Limiter Spool (2) Load Sensing Spool (3) Check Valve (4)
Valve base (5) Oil Passages:
Oil supply from pump (6)
Pressure Limiter to Case Drain (7) To Displacement Control Piston (8) Pump Control Valve to Case Drain (9) Transfer Pump Drive and Mounting (10) Pump Control Valve (11)
INSTRUCTOR NOTE: The Compensator Valve is an emissions device and should not be adjusted.
82 • Hydraulic supply pump circuit TO LUBE SYSTEM PUMP CONTROL VALVE OIL FILTER
3408E/3412E HEUI FUEL SYSTEM
HYDRAULIC SYSTEM OPERATION
OIL COOLER LUBE OIL PUMP HEUI HEUI OIL SUMP HYDRAULIC PRESSURE SENSOR HYDRAULIC TEMPERATURE SENSOR OIL PRESSURE SENSOR HYDRAULIC SUPPLY PUMP GROUP COOL DOWN CIRCUIT FUEL TANK FUEL TEMPERATURE SENSOR PRESSURE REGULATING VALVE SECONDARY FUEL FILTER FUEL TRANSFER PUMP FLUID MANIFOLD HYDRAULIC PASSAGE COLD START OIL RESERVOIR PRIMARY FUEL FILTER ECM FLUID MANIFOLD HYDRAULIC PASSAGE System Operation
As stated earlier, the Hydraulic Supply Pump Group combines the functions of the high pressure oil pump, the fuel transfer pump, and the pump control valve into a single unit. The function of the Hydraulic Supply Pump Group is to provide the required oil flow at the desired pressure to operate the injectors, provide the supply of low pressure fuel required for refilling the injectors after each injection, and for ECM cooling.
As the oil is supplied by the pump rotating group, the pressure is raised from the reservoir level of approximately 415 kPa (60 psi) to the pressure required for injector operation. Depending on the engine rating, the operating conditions, and the engine mapping characteristics, this pressure is controlled between 5000 and 22800 kPa (725 and 3300 psi).
83 • Conditions during START-UP • Displacement varied by changing swashplate angle • Swashplate at full displacement during start-up
• Pump control valve solenoid energized TO LUBE SYSTEM TO RIGHT OIL MANIFOLD TO LEFT OIL MANIFOLD COLD START RESERVIOR OIL SUMP PUMP CONTROL VALVE LOAD SENSING SPOOL PRESSURE LIMITER SPOOL PUMP CASE DRAIN SOLENOID (ENERGIZED) DISPLACEMENT CONTROL PISTON
HEUI HYDRAULIC CONTROL SYSTEM
START-UP
CHECK VALVE
SUPPLY PUMP
The displacement of the pump is controlled to maintain the desired operating pressure at the flow rate required by the injectors. The displacement is regulated by an electro-hydraulic control.
Displacement of the pump is varied by pivoting the swashplate from 0 degrees to a maximum angle of 15.5 degrees. When the engine is not running, the swashplate is at the maximum angle. During operation, the displacement control piston adjusts the swashplate position to meet the system flow demand.
During initial cranking, the swashplate is at full displacement until the supply pressure increases to 6200 kPa (900 psi). The spring at the end of the load sensing spool regulates this pressure. Then, the specification programmed into the ECM for normal cranking will override this
pressure. Until this point, the control valve solenoid is fully energized for the pressure increase.
84
• Compensator valve conditions during START-UP
• Displacement control piston vented to case drain
PRESSURE LIMITER SPOOL
CHECK VALVE PUMP CONTROL VALVE DRAIN ORIFICE ORIFICE TO CASE DRAIN
LOAD SENSING SPOOL
FROM DISPLACEMENT CONTROL PISTON REVERSE FLOW CHECK VALVES START-UP
COMPENSATOR ASSEMBLY
TO CASE DRAINDuring START-UP, pressure from the pump enters the compensator assembly. The Pump Control Valve is energized for quick pressure build-up.
Pressure is felt at both ends of the Load Sensing Spool. The spool is shifted to the right and oil from the Displacement Control Piston is vented to case drain. The swashplate is at maximum angle.
The drain orifice below the Pump Control Valve provides a small amount of restriction to improve valve stability.
85
• Conditions during DESTROKE
• Pump control valve solenoid de-energized
• Pump control valve changes pump displacement TO LUBE SYSTEM TO RIGHT OIL MANIFOLD TO LEFT OIL MANIFOLD COLD START RESERVIOR OIL SUMP PUMP CONTROL VALVE LOAD SENSING SPOOL PRESSURE LIMITER SPOOL PUMP CASE DRAIN SOLENOID (DE-ENERGIZED)
HEUI HYDRAULIC CONTROL SYSTEM
DESTROKE
CHECK VALVE DISPLACEMENT
CONTROL PISTON
SUPPLY PUMP
After the engine starts and pressure increases, the ECM will signal the control valve to match the actual with the desired pressure by
momentarily de-energizing and then regulating the current flow to the pump control valve solenoid.
The decrease in current applied to the pump control valve solenoid lowers the pressure required to initiate flow through the pump control valve. This lower cracking pressure on the pump control valve creates a force imbalance on the load sensing spool, causing the spool to move toward the spring end of the compensator. This spool motion connects the displacement control piston to pump output flow, allowing the swashplate to decrease the displacement of the pump. The decreased displacement lowers the pump output to the pressure level required by the ECM.
86 • Compensator valve conditions during DESTROKE • Displacement control piston pressurized PUMP CONTROL VALVE DRAIN ORIFICE TO DISPLACEMENT CONTROL PISTON TO CASE DRAIN PRESSURE LIMITER SPOOL CHECK VALVE ORIFICE LOAD SENSING SPOOL DESTROKE
COMPENSATOR ASSEMBLY
During DESTROKE, the ECM momentarily de-energizes the Pump Control Valve causing a pressure drop in the spring chamber of the Load Sensing Spool.
Unbalanced pressures force the spool to the left, allowing the oil to enter the Displacement Control Piston and move the swashplate toward minimum angle.
87
• Conditions during UPSTROKE
• Pump control valve energized TO LUBE SYSTEM TO RIGHT OIL MANIFOLD TO LEFT OIL MANIFOLD COLD START RESERVIOR OIL SUMP PUMP CONTROL VALVE LOAD SENSING SPOOL PRESSURE LIMITER SPOOL PUMP CASE DRAIN SOLENOID (ENERGIZED)
HEUI HYDRAULIC CONTROL SYSTEM
UPSTROKE
CHECK VALVE DISPLACEMENT
CONTROL PISTON
SUPPLY PUMP
As the load on the engine increases and higher pressure is required, the ECM will signal the control valve to increase pressure by increasing the current flow to the pump control valve solenoid.
The increase in current applied to the pump control valve solenoid raises the pressure setting of the pump control valve. This higher pressure at the pump control valve creates a force imbalance on the load sensing spool, causing the spool to move toward the supply signal line end of the compensator. This spool motion vents the displacement control piston to case drain, allowing the spring to move the swashplate to increase the displacement of the pump. The increased displacement raises the pump output to the desired pressure level required by the ECM.
88 • Compensator valve positions during UPSTROKE • Displacement control piston is drained PRESSURE LIMITER SPOOL CHECK VALVE ORIFICE LOAD SENSING SPOOL PUMP CONTROL VALVE DRAIN ORIFICE FROM DISPLACEMENT CONTROL PISTON TO CASE DRAIN UPSTROKE
COMPENSATOR ASSEMBLY
As the load is applied to the engine, the ECM increases current to the Pump Control Valve.
Pressure is felt at both ends of the Load Sensing Spool. The spool moves to the right (due to spring force) and oil from the Displacement Control Piston is vented to case drain, which allows the swashplate to
89
• Pressure limiter operation
• Check engine lamp indicates the fault
• Pump control valve test TO LUBE SYSTEM TO RIGHT OIL MANIFOLD TO LEFT OIL MANIFOLD COLD START RESERVIOR OIL SUMP PUMP CONTROL VALVE LOAD SENSING SPOOL PRESSURE LIMITER SPOOL PUMP CASE DRAIN SOLENOID (DE-ENERGIZED)
HEUI HYDRAULIC CONTROL SYSTEM
PRESSURE LIMITER OPERATION
DISPLACEMENT CONTROL PISTON
SUPPLY PUMP
PLUGGED ORIFICE
If the load sensing spool or pump control valve sticks or otherwise malfunctions to create higher than desired operating pressures, the maximum pressure limiter spool is utilized. In this schematic, a plugged orifice is simulated. (This example represents an actual condition which was caused by debris being introduced during a field replacement of the compensator valve.)
The Pressure Limiter Spool directs pump outlet flow to the displacement control piston and reduces the stroke of the pump if the system pressure exceeds 25600 kPa (3700 psi).
During these conditions, the pump will develop 24800 to 25600 kPa (3600 to 3700 psi) maximum pressure, regardless of the desired hydraulic pressure. The Check Engine Lamp will be ON, indicating a fault. A Pump Control Valve Test will verify the control valve operation. This test enables the technician to manually ramp the pressure up and down using the ET service tool. This procedure will also be useful when evaluating the condition of the hydraulic system.
90 • Pressure limiter operation • Pressure limiter directs pressure to control piston PRESSURE LIMITER SPOOL CHECK VALVE ORIFICE LOAD SENSING SPOOL PUMP CONTROL VALVE DRAIN ORIFICE TO DISPLACEMENT CONTROL PISTON TO CASE DRAIN PLUGGED ORIFICE
PRESSURE LIMITER OPERATION
COMPENSATOR ASSEMBLY
If the supply pressure exceeds 25600 kPa (3700 psi), the force acts on the Pressure Limiter Spool and shifts it to the left. This movement
compresses the spring and allows oil to unseat the check valve and pressurize the displacement control piston. The swashplate moves to minimum angle to decrease flow and limit system pressure.
91
• Pump control valve
• Flow controlled by compensator and pump control valve
ADAPTER CAGE RING SHELL PIN STATOR SEAL SEAT POPPET VALVE SOLENOID ARMATURE STOP TO CASE DRAIN FROM LOAD SENSING SPOOL VALVE VALVE BLOCK NO CURRENT FLOW COIL ASSEMBLY
PUMP CONTROL VALVE
EDGE FILTER
SPRING RETAINER
The pump control valve is mounted on the compensator control assembly which contains the load sensing spool and the pressure limiter. In this slide, the pump control valve is open, allowing pressure to vent to case drain.
Flow to and from the displacement control piston is determined by the compensator control assembly and the pump control valve. The compensator control assembly senses pump output pressure through a pilot pressure signal line. The pump control valve varies the pressure to the displacement control piston by varying the pressure on one end of the load sensing spool valve.
The load sensing spool directs oil to and from the displacement control piston. The spool has a hole through its center, which allows pilot pressure to reach both ends of the spool. The spring force on the load sensing spool is adjusted at the factory. The pump will develop 5000 kPa (725 psi) with the pump control solenoid valve disconnected while
92
• Pump control valve
• High current flow equals high pressure
ADAPTER CAGE RING SHELL PIN STATOR SEAL SEAT POPPET VALVE SOLENOID ARMATURE STOP CASE DRAIN VALVE BLOCK COIL ASSEMBLY
HIGH CURRENT FLOW
PUMP CONTROL VALVE
EDGE FILTER SPRING RETAINER FROM LOAD SENSING SPOOL VALVE
The pressure level in the hydraulic operating supply is monitored by a hydraulic pressure sensor. When the hydraulic pressure is less than desired (as determined by the ECM), the current level applied to the pump control valve solenoid is increased.
The increase in current to the solenoid raises the pressure required to initiate flow through the pump control valve. This higher cracking pressure for the pump control valve creates a force imbalance on the load sensing spool, causing the load sensing spool to move toward the supply signal line end of the spool. This spool motion vents the displacement control piston to pump case drain, allowing the swashplate to increase displacement of the pump.
The increased displacement raises the hydraulic output to the rate required by the ECM for the injectors.
INSTRUCTOR NOTE: To reinforce this presentation, the following tasks may be demonstrated on an engine:
Hydraulic pump priming
Remove and install a pump control valve and the compensator valve assembly.
Check the following using the status screen: - Desired hydraulic pressure
- System hydraulic oil pressure - System hydraulic oil temperature
- Percentage current to pump control valve
Using the ET Injection Actuation Pressure Test, check the pump and pump control valve operation, and check for correct
pressures throughout the range.
Physically check for leaks externally and internally below the valve covers (injectors must be disabled during cranking with the valve covers removed).
