6 KENR6908
Troubleshooting Section
Electronic Cont rols
The electronic system consists of the following
components: the ECM, the Mechanically Actuated
Electronical
ly Controlled Unit Injectors (MEUI), the
wiring harness, the switches, and the sensors. The
ECM is the computer. The flash file is the software
for the compu
ter. The flash file contains the operating
maps. The operating maps defi ne the following
characteristics of the engine:
•
Horsepower
•
Torque curve
s
TheECMdeterminesthetimingandtheamountof
fuel that is d
elivered to the cylinders. These decisions
are based on the actual conditions and/or on the
desired conditions at any given time.
The ECM compares the desired engine speed to
the actual engine speed. The actual engine speed is
determined
through the engine speed/timing sensor.
The desired engine speed is determined with the
following factors:
•
Throttle signal
•
Other input
signals from sensors
•
Certain diagnostic codes
If the desired engine speed is greater than the actual
engine speed, the ECM injects more fuel in order to
increase t
he actual engine speed.
Fuel Injection
The ECM controls the amount of fuel that is injected
by varying the signals to the injectors. The injector will
pump fuel o
nly if the injector solenoid is energized.
The ECM sends a high voltage signal to the solenoid.
This high voltage signal energizes the solenoid. By
controll
ing the timing and the duration of the high
voltage signal, the ECM can control injection timing
and the ECM can control the amount of fuel that is
injected
.
The ECM limits engine power during cold mode
operati
on and the ECM modifies injection timing
during cold mode operation. Cold mode operation
provides the following benefits:
•
Increased cold weather starting capability
•
Reduced
warm-up time
•
Reduced white smoke
Cold mode is activated whenever the engine
temperature fa
lls below a predetermined value. Cold
mode remains active until the engine temperature
rises above a predetermined value or until a time
limit is excee
ded.
The flash file inside the ECM sets certain limits on
the amount of
fuel that can be injected. The “FRC
Fuel Limit” is used to control the air/fuel ratio for
control of emissions. The “FRC Fuel Limit” is a limit
that is based
on the turbocharger outlet pressure.
A higher turbocharger outlet pressure indicates that
thereismoreairinthecylinder.WhentheECM
senses a hig
her turbocharger outlet pressure, the
ECM increases the “FRC Fuel Limit”. When the ECM
increases the “FRC Fuel Limit”, the ECM allows
more fuel in
to the cylinder. The “FRC Fuel Limit” is
programmed into the ECM at the factory. The “FRC
Fuel Limit” cannot be changed.
The “Rated Fuel Limit” is a limit that is based on the
power rating of the engine and on engine rpm. The
“Rated Fue
l Limit” is similar to the rack stops and to
the torque spring on a mechanically governed engine.
The “Rated Fuel Limit” provides the power curves
and the to
rque curves for a specific engine family and
for a specific engine rating. The “Rated Fuel Limit” is
programmed into the ECM at the factory. The “Rated
Fuel Limi
t” cannot be changed.
Once the ECM determines the amount of fuel that
is requir
ed, the ECM must determine the timing of
the fuel injection. The ECM uses the signal from the
camshaft position sensor to calculate the top center
positio
n of each cylinder . The ECM decides when
fuel injection should occur relative to the top center
position and the ECM provides the signal to the
inject
or at the desired time. The ECM adjusts timing
for optimum engine performance, for optimum fuel
economy, and for optimum control of white smoke.
Programmable Parameters
Certain parameters that affect the engine operation
may be changed with the Perkins Electronic
Servic
e Tool (EST). The parameters are stored
in the ECM, and some parameters are protected
from unauthorized changes by passwords. These
passw
ords are called factory passwords.
Passw
ords
Several system configuration parameters and most
logge
d events are protected by factory passwords.
Factory passwords are available only to Perkins
dealers and distributors. Refer to Troubleshooting,
“Fac
tory Passwords” for additional information.
This document has been printed from SPI². Not for Resale
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