1 ENGINE SYSTEMS 27
High-Pressure Oil Flow
The oil reservoir in the front cover provides a constant
supply of oil to a high-pressure oil pump m ounted to
the backside of the front cover. Oil drawn from the oil
reservoir is constantly refilled by the eng ine lubrication
system.
The gear-driven, high-pressure oil pump delivers oil
through a high-pressure o il hose, t hrough 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 energiz ed . Exhaust oil exits t hrough
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
TheICPisaclosedloopsystemthatusestheICP
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.
ICP System Control
Figure 21 ICP control
ICP Operation
The IPR solenoid receives a pulse-
width modulated
signal from the ECM that indicate
s the on and off time
the control valve is e nergize
d. The pulse is calibrated
to control ICP pressure in a r
ange from 5 MPa (725
psi) up to 28 MPa (4, 075 psi).
Maximum p ress ure
relief occurs at about 32 MP
a (4,600 psi).
TheIPRvalveismountedint
he body of the
high-pressure pump. The IP
R valve maintains
the desired ICP by dumpi
ng excess oil back to the
crankcase sump.
As demand for ICP increa
ses, the ECM increases the
pulse-width modulatio
n to the IPR solenoid. When
ICP demand decreases,
the ECM decreases the duty
cycle to the solenoid
, a llowing mo re oil to flow from the
drain orifice.
The ECM sets Diagnos
tic Trouble Codes (DTCs),
if the ICP electric
al signal is out-of-range. DTCs
arealsosetifanIC
P s ignal corresponds to an
out-of-range val
ue for injection control pressure for a
given operating
condition.
The ECM will igno
re ICP signals that are out-of-range
and the IPR valv
e will operate from programmed
default values
. This is called Open Loop operation.
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
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