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Part 4 of 6 in a series of articles outlining the Features, Descriptions, Unique Service Procedures, and General Diagnostics of the 6.0L DIT Power Stroke
From International Truck & Engine Corporation Publication
6.0 DIT Power Stroke
Fuel Management System
Generation II Fuel Management System Diagram
The generation II fuel management system uses high pressure oil and
electronics to actuate and control fuel injection into the cylinders.
Generation II Fuel Management System Major Components
The fuel management system is comprised of several sub systems.
Fuel Supply System.
High Pressure Oil System.
Generation II Fuel Management System Advantages
Emissions and noise have been reduced through improvements in rate and
No external high pressure oil lines exist.
The high pressure system's pressure relief is located in the IPR (Injection
High Pressure Oil System Flow
Oil reservoir is filled by the lube oil system and contains approximately 1
High pressure pump is sealed inside the crankcase, and has only one (1)
High pressure pump discharge line connects the pump to the left and right
branches and to the IPR valve in the high pressure pump cover.
High pressure oil stand pipe connects to the branch outlets and provides a
path through the pushrod area to the high pressure lines.
High pressure oil line connects the stand pipes to the high pressure oil
High pressure oil rail is bolted to the cylinder heads and acts as a
reservoir for high pressure oil.
Check valves incorporated in the inlet fitting for the high pressure oil
rail, limit hydraulic disturbance/feed back from injector operation.
Injectors deliver fuel when the spool valve is positioned to allow oil to
enter the area above the intensifier piston.
High Pressure Oil System Schematic
After lube oil is cooled and filtered, some is directed to the reservoir.
The reservoir provides oil to the high pressure pump.
The IPR (Injection Pressure Regulator) is PCM-controlled and contains the
system's pressure relief valve which opens at 4000 psi.
The plumbing from the pump to the high pressure oil rails for each head
contains a check valve and orifice.
The oil rails are not cast into the head but are removable and fastened to
the cylinder head and connected to the top of the injectors.
High Pressure Pump & Cover
The high pressure pump is installed inside the crankcase.
The pump is a seven (7) piston swash plate style pump that is driven off of
the rear gear train.
Minor leakage from the pump will not create external oil leaks.
Both banks of cylinders are supplied oil through one (1) pump outlet.
IPR (Injection Control Pressure Regulator) & ICP (Injection Control Pressure
The IPR and ICP are both installed into the high pressure pump cover,
beneath the turbocharger turbine inlet pipe.
High Pressure Oil with AWA Feature
The high pressure oil rail has special AWA (Acoustic Wave Attenuation)
features to dampen hydraulic noises.
To accomplish this, an AWA fitting is placed in the center of the high
pressure oil rail and two specially designed end caps are used.
Fuel Injector Features
The injector uses two (2) 48 volt 20 amp coils to control a spool valve that
directs oil flow in and out of the injector.
The injector coils are turned on for approximately 800 µsec (micro second or
millionth of a second.
No special tools are needed to remove the injectors from their bore.
The injector is slowly removed from its bore by removing the hold down clamp
Injector & O-rings
The injector has two (2) replaceable o-rings on the outside of the body, one
(1) internal non-replaceable o-ring in the top of the injector, and one (1)
replaceable copper combustion gasket on the tip of the injector.
The injector's two (2) coils have a single four (4) pin connector that
passes through the rocker arm carrier.
Injector Coils & Spool Valve
There is an open coil and a close coil on the injector that moves the spool
valve from side to side using magnetic force.
The spool valve has two positions; when the valve is in the open position,
it allows oil to flow from the high pressure oil rail into the injector.
When the valve is in the closed position, it allows oil to drain from the
injector back to the crankcase.
The total movement of the valve is only .017".
When the spool valve is in the open position, high pressure oil is allowed
to enter the injector and pushes the intensifier piston and plunger downward.
Since the intensifier piston is 7.1 times greater in surface area than the
plunger, the injection force is also 7.1 times greater at the plunger than what
the injection control pressure (ICP) is.
Plunger & Barrel
The bottom of plunger and barrel of the injector is where the fuel injection
pressure is built.
When the plunger is pushed downward by the intensifier piston, it increases
the fuel pressure in the barrel 7.1 times that of the ICP pressure.
The plunger is coated with a tungsten carbide coating to reduce the
possibility of scuffing and poor performance.
The injection nozzle needle is an inwardly opening type which lifts off its
seat when pressure overcomes the VOP (Valve Opening Pressure) of approximately
Fuel is atomized at high pressure through the nozzle tip.
Stages of Injection
The injection cycle has three (3) stages.
End of main injection.
During some conditions, the injector will perform all three stages of the
injection cycle two times per firing cycle. This is called pilot
During the fill stage, the spool valve is in the closed position.
High pressure oil from the oil rail is dead headed at the spool valve.
Low pressure fuel fills the port below the plunger.
The needle control spring holds the needle on its seat so that fuel cannot
enter the combustion chamber.
Main Injection Step 1
Pulse width controlled current energizes the open coil, magnetic force moves
the spool valve to the open position.
High pressure oil flows past the spool valve into the intensifier piston
Oil pressure overcomes the intensifier piston spring force and the
intensifier starts to move.
Fuel inlet check ball seats due to an increase of fuel pressure under the
Fuel pressure starts to build once the plunger passes the fuel spill port of
Force on the nozzle needle begins to build.
Main Injection Step 2
The pulse width-controlled current is shut off after 800 µsec (micro second
or millionth of a second) but the spool remains in the open position.
High pressure oil from the rail continues to flow past the spool valve.
The intensifier piston and plunger continue to move and pressure increases
in the barrel.
When fuel pressure rises above the VOP (Valve Opening Pressure) of about
3100 psi, the nozzle needle lifts off of its seat and injection begins.
End of Main Injection Step 1
When the IDM (Injector Drive Module) determines that the correct injector on
time has been reached (meaning that the correct amount of fuel has been
delivered), it sends a pulse width-controlled current to the close coil of the
The current energizes the close coil. Magnetic force moves the spool
valve to the closed position.
High pressure oil is dead headed against the spool valve.
End of Main Injection Step 2
The pulse width-controlled current is shut off after 800 µsec (micro seconds
or millionth of a second) but the spool remains in the closed position.
The intensifier piston and plunger begin to return to their initial
Oil above the intensifier piston flows past the spool valve through the
Fuel pressure decreases until the nozzle needle control spring forces the
needle back onto its seat.
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