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AJ-V8/5HP24
58
Engine Management
Fuel Injection
The ECM operates eight injectors to provide the
engine with fuel. The amount of fuel required is
determined from a base air:fuel ratio which is
then adjusted for specific operating conditions.
The ECM varies the number and duration of
injector pulses per engine cycle to regulate the
fuel flow. Injector timing is synchronised with
engine rotation, except during starting and
acceleration.
Feedback signals from the two HO2S in the
vehicle's exhaust system enable the ECM to
exercise closed loop fueling control and adaptive
fueling. Separate channels in the ECM control
each bank of injectors.
Adaptive fueling accommodates engine efficiency
variations, system tolerances and engine ageing.
Adaptations are produced at idle speed and four
other points through the RPM/load range, on a
fully warm engine, when the adaptive fueling
function centralizes the feedback range. The ECM
retains the adaptations in memory, for use in
subsequent driving cycles. If the difference
between the new and previous adaptations is
excessive, a DTC is logged in the ECM memory.
If the battery supply to the ECM is disrupted (eg.
battery disconnection), the adaptations are lost
from memory. On restoration of the battery
supply, engine operation may be uneven until the
adaptations are restored, especially at idle speed.
An output from the ECM controls the relay that
operates the fuel pump. At ignition on, the pump
will operate for 2 seconds without the ignition
switch being set to crank, after which time the
pump will be de-energized. Similarly, if the engine
stops with the ignition on, the pump will be de-
energized after 2 seconds. The pump operates
continuously while the ignition switch is set to
crank, or to on with the engine running.
FUEL PUMP CONTROL
B+ Battery
B+ Ignition
Fuel Pump
Relay
Trunk
Fuse Box
ECM
Fuel Pump
F7
303-134
Fuel Pump
The two O2S in the vehicle's exhaust system
provide inputs which enable the ECM to monitor
the efficiency of the downpipe catalytic
converters. These inputs also enable the ECM to
modify the HO2S inputs, to optimise the life of
the catalytic converters.
Base Fuel Map
The ECM contains a base fuel map that corrects
the base air:fuel ratio to the optimum mixture for
a nominal engine throughout the engine speed
and load ranges.
Battery Voltage Correction
Fuel flow through the injectors changes with
voltage, so the ECM monitors their supply
voltage and compensates for any variation from
the nominal.
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