Navistar International DT 466 Diagnostic/Troubleshooting Manual page 31

High-Pressure Oil Flow
The oil reservoir in the front cover provides a constant
supply of oil to a high-pressure oil pump mounted to
the backside of the front cover. Oil drawn from the oil
reservoir is constantly refilled by the engine lubrication
system.
The gear-driven, high-pressure oil pump delivers oil
through a high-pressure oil hose, through a cylinder
head passage into the high-pressure oil manifold
beneath the valve cover. The manifold distributes to
the top of each fuel injector.
When the OPEN coil for each injector is energized, the
injectors use high-pressure oil to inject and atomize
fuel in the combustion chambers. To end injection, the
CLOSE coils are energized. Exhaust oil exits through
two ports in the top of the fuel injectors, then drains
back to sump.
Injection Control Pressure (ICP) Closed Loop
System
Figure 20 ICP closed loop system
The ICP is a closed loop system that uses the ICP
sensor to provide feedback to the ECM. The ECM
uses the ICP sensor to continuously monitor injection
control pressure and adjust the duty cycle of the IPR
valve to match engine requirements.
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
1 ENGINE SYSTEMS
ICP System Control
Figure 21
ICP Operation
The IPR solenoid receives a pulse-width modulated
signal from the ECM that indicates the on and off time
the control valve is energized. The pulse is calibrated
to control ICP pressure in a range from 5 MPa (725
psi) up to 28 MPa (4,075 psi). Maximum pressure
relief occurs at about 32 MPa (4,600 psi).
The IPR valve is mounted in the body of the
high-pressure pump.
the desired ICP by dumping excess oil back to the
crankcase sump.
As demand for ICP increases, the ECM increases the
pulse-width modulation to the IPR solenoid. When
ICP demand decreases, the ECM decreases the duty
cycle to the solenoid, allowing more oil to flow from the
drain orifice.
The ECM sets Diagnostic Trouble Codes (DTCs),
if the ICP electrical signal is out-of-range.
are also set if an ICP signal corresponds to an
out-of-range value for injection control pressure for a
given operating condition.
The ECM will ignore ICP signals that are out-of-range
and the IPR valve will operate from programmed
default values. This is called Open Loop operation.
EGES-270-1
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
ICP control
The IPR valve maintains
27
DTCs