Figure 16 Fuel management system
The fuel management system includes the following:
• Lubrication system
• Injection Control Pressure (ICP) system
• Engine Compression Brake (ECB)
• Fuel supply system
• Fuel injectors
• Electronic control system
ICP System
Figure 17 Injection Control Pressure (ICP) system
High-Pressure Oil Flow
The lubrication system supplies the oil reservoir located in the front cover. The reservoir provides oil for the high-pressure oil pump. The pump is mounted on the backside of the front cover and is gear driven by the upper idler gear.
High-pressure oil is directed to the high-pressure oil hose, cylinder head passage, and high-pressure oil manifold.
High-pressure oil is used by the fuel injectors to pressurize and inject fuel in the cylinders. This occurs when the OPEN coil for each fuel injector is energized.
Excess high-pressure oil is directed to the crankcase sump by the Injection Pressure Regulator (IPR) valve.
The IPR valve is controlled by the Electronic Control Module (ECM) to maintain a desired injection control pressure.
If equipped with the optional engine brake, some high-pressure oil is directed internally to the engine brake pistons when the engine compression brake is activated. Since these two systems share a common gallery, a problem with the engine compression brake system can adversely affect injection control pressure and vise versa.
ICP Closed Loop System
Figure 18 ICP closed loop system
The ICP (Injection Control Pressure) system is a closed loop system that uses the ICP sensor to continuously provide feedback to the ECM. The ECM
commands the IPR duty cycle to adjust pressure to match engine requirements.
ICP Control System
Figure 19 ICP control system
The IPR valve receives a Pulse Width Modulated (PWM) signal from the ECM. This controls the on and off time the IPR valve is energized. The on/off time is controlled by the ECM to meet calibrated desired values.
The IPR valve is mounted in the body of the high-pressure pump. The IPR valve maintains desired ICP by dumping excess oil back into the crankcase sump.
As demand for ICP increases, the ECM increases the current to the IPR valve solenoid. When demand for ICP decreases, the duty cycle to the IPR valve decreases and more oil is allowed to flow back to the crankcase sump.
When the ICP electrical signal is out-of-range, the ECM sets a fault code.
When ICP signals are out-of-range, the ECM ignores them and goes into open loop operation. The IPR valve will operate from programmed default values.
The ICP sensor is installed in the high-pressure oil manifold under the valve cover.
Fuel Injector
Figure 20 Fuel injector 1. Upper O-ring
2. Lower O-ring 3. Nozzle gasket 4. Injector nozzle 5. Fuel inlet port
Fuel Injector Features
Two 50 volt, 25 amp coils control a spool valve that directs oil flow in and out of the injector. Each injector has a single four pin connector that connects to the valve cover gasket assembly.
Injector Coils and Spool Valve
An OPEN coil and a CLOSE coil on the injector move the spool valve from side to side using magnetic force.
The spool has two positions:
• When the spool valve is open, oil flows into the injector from the high-pressure oil manifold.
• When the spool valve is closed, oil exits from the top of the fuel injector and drains back to the crankcase.
Intensifier Piston and Plunger
When the spool valve is open, high-pressure oil enters the injector, pushing down the intensifier piston and plunger. Since the intensifier piston is 10 times greater in surface area than the plunger, the fuel injection pressure is also 10 times greater than injection control pressure on the plunger.
Plunger and Barrel
Fuel pressure builds at the base of the plunger in the barrel. When the intensifier piston pushes the plunger down, the plunger increases fuel pressure in the barrel 10 times greater than injection control pressure. The plunger has a hardened coating to resist scuffing.
Injector Needle
The injector needle opens inward when fuel pressure overcomes the Valve Opening Pressure (VOP). Fuel is atomized at high-pressure through the nozzle tip.
Fuel Injector Operation
The injector operation has three stages:
• Fill stage
• Injection
• End of injection
Figure 21 Fuel injector cross section
Low-pressure fuel fills the four ports and enters through the edge filter on its way to the chamber beneath the plunger. The needle control spring holds the needle onto its seat to prevent fuel from entering the combustion chamber.
Injection
1. A pulse-width controlled current energizes the OPEN coil. Magnetic force moves the spool valve open. High-pressure oil flows past the spool valve and onto the top of the intensifier piston. Oil pressure overcomes the force of the intensifier piston spring and the intensifier starts to move down. An increase in fuel pressure under the plunger seats the fuel inlet check ball, and fuel pressure starts to build on the needle.
2. The pulse-width controlled current to the OPEN coil is shut off, but the spool valve remains open. High-pressure oil from the high-pressure oil manifold continues to flow past the spool valve. The intensifier piston and plunger continue to move and fuel pressure increases in the barrel. When fuel pressure rises above the VOP, the needle lifts off its seat and injection begins.
End of Injection
1. When the ECM determines that the correct injector on-time has been reached (the correct amount of fuel has been delivered), the ECM sends a pulse-width controlled current to the CLOSE coil of the injector.
The current energizes the CLOSE coil and magnetic force closes the spool valve.
High-pressure oil is stopped against the spool valve.
2. The pulse-width controlled current to close the coil is shut off, but the spool valve remains closed. Oil above the intensifier piston flows past the spool valve through the exhaust ports. The intensifier piston and plunger return to their initial positions. Fuel pressure