Perkins 1104D NH1 Systems Operation Testing And Adjusting page 33

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At start-up, the ECM determines the top center
position of the number 1 cylinder from the secondary
speed/timing sensor in the fuel injection pump.
The ECM decides when fuel injection should occur
relative to the top center position. The ECM optimizes
engine performance by control of each of the
electronic unit injectors so that the required amount
of fuel is injected at the precise point of the engine's
cycle. The electronic unit injectors are supplied high
pressure fuel from the fuel injection pump. The ECM
also provides the signal to the solenoid in the fuel
injection pump. The solenoid in the fuel injection
pump controls a valve in the fuel injection pump. This
valve controls the pressure in the fuel injection pump.
Fuel that is not required for the engine is diverted
away from the fuel injection pump back to the fuel
tank.
The ECM adjusts injection timing and fuel pressure
for the best engine performance, the best fuel
economy and the best control of exhaust emissions.
The actual timing can be viewed with an electronic
service tool. Also, the desired timing can be viewed
with an electronic service tool.
Fuel Injection
The personality module software inside the ECM
sets certain limits on the amount of fuel that can be
injected.
The FRC Limit is a limit that is based on intake
manifold air pressure and engine rpm. The FRC
Limit is used to control the air/fuel ratio in order to
control the engine's exhaust emissions. When the
ECM senses a higher intake manifold air pressure,
the ECM increases the FRC Limit. A higher intake
manifold air pressure indicates that there is more air
in the cylinder. When the ECM increases the FRC
Limit, the ECM allows more fuel into the cylinder.
The Rated Fuel Limit is a limit that is based on the
power rating of the engine and on the engine rpm.
The Rated Fuel Limit enables the engine power and
torque outputs to conform to the power and torque
curves of a specific engine model.
These limits are in the personality module and these
limits cannot be changed.
Diagnostic Codes
When the ECM detects an electronic system problem,
the ECM generates a diagnostic code. Also, the ECM
logs the diagnostic code in order to indicate the time
of the problem's occurrence. The ECM also logs the
number of occurrences of the problem. Diagnostic
codes are provided in order to indicate that the ECM
has detected an electrical problem or an electronic
problem with the engine control system. In some
cases, the engine performance can be affected when
the condition that is causing the code exists.
If the operator indicates that a performance problem
has occurred, the diagnostic code may indicate the
cause of the problem. Use a laptop computer to
access the diagnostic codes. The problem should
then be corrected.
Event Codes
Event Codes are used to indicate that the ECM has
detected an abnormal engine operating condition.
The ECM will log the occurrence of the event code.
This does not indicate an electrical malfunction or
an electronic malfunction. If the temperature of the
coolant in the engine is higher than the permitted
limit, then the ECM will detect the condition. The
ECM will then log an event code for the condition.
Passwords
System Configuration Parameters are protected by
factory passwords. This will prevent unauthorized
reprogramming of the system and the unauthorized
removal of logged events. Factory passwords are
calculated on a computer system that is available
only to Perkins distributors. Since factory passwords
contain alphabetic characters, only an electronic
service tool may change System Configuration
Parameters. System Configuration Parameters affect
the power rating or the emissions. Passwords also
allow the customer to control certain programmable
engine parameters.
Refer to Troubleshooting, "Programming Parameters"
and Troubleshooting, "Factory Passwords".
Speed/Timing Sensor
Illustration 34
Timing wheel on the crankshaft
Systems Operation Section
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