1997 MITSUBISHI TRITON fuel pressure

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MITSUBISHI TRITON 1997 Workshop Manual MPI ± General Information13A-3
MULTIPOINT FUEL INJECTION (MPI)13100010265
GENERAL INFORMATION
The Multipoint Fuel Injection System consists
of sensors which detect the engine conditions,
the engine-E

MPI ± General Information13A-3
MULTIPOINT FUEL INJECTION (MPI)13100010265
GENERAL INFORMATION
The Multipoint Fuel Injection System consists
of sensors which detect the engine conditions,
the engine-ECU which controls the system
based on signals from these sensors, and
actuators which operate under the control of
the engine-ECU. The engine-ECU carries outactivities such as fuel injection control, idle
speed control and ignition timing control. In
addition, the engine-ECU is equipped with
several diagnosis modes which simplify
troubleshooting when a problem develops.
FUEL INJECTION CONTROL
The injector drive times and injector timing are
controlled so that the optimum air/fuel mixture
is supplied to the engine to correspond to the
continually-changing engine operation condi-
tions.
A single injector is mounted at the intake port
of each cylinder. Fuel is sent under pressure
from the fuel tank by the fuel pump, with the
pressure being regulated by the fuel pressure
regulator. The fuel thus regulated is distributed
to each of the injectors.
Fuel injection is normally carried out once for
each 2-cylinder group for every two rotationsof the crankshaft. This is called group fuel
injection. The engine-ECU provides a richer
air/fuel mixture by carrying out ªopen-loopº
control when the engine is cold or operating
under high load conditions in order to maintain
engine performance. In addition, when the
engine is warm or operating under normal
conditions, the engine-ECU controls the air/fuel
mixture by using the oxygen sensor signal to
carry out ªclosed-loopº control in order to obtain
the theoretical air/fuel mixture ratio that
provides the maximum cleaning performance
from the three way catalyst.
IDLE AIR CONTROL
The idle speed is kept at the optimum speed
by controlling the amount of air that bypasses
the throttle valve in accordance with changes
in idling conditions and engine load during
idling. The engine-ECU drives the idle speed
control (ISC) motor to keep the engine running
at the pre-set idle target speed in accordance
with the engine coolant temperature and airconditioner load. In addition, when the air
conditioner switch is turned off and on while
the engine is idling, the ISC motor operates
to adjust the throttle valve bypass air amount
in accordance with the engine load conditions
in order to avoid fluctuations in the engine
speed.
IGNITION TIMING CONTROL
The power transistor located in the ignition
primary circuit turns ON and OFF to control
the primary current flow to the ignition coil. This
controls the ignition timing in order to provide
the optimum ignition timing with respect to theengine operating conditions. The ignition timing
is determined by the engine-ECU from the
engine speed, intake air volume, engine coolant
temperature and atmospheric pressure.
SELF-DIAGNOSIS FUNCTION
When an abnormality is detected in one
of the sensors or actuators related to
emission control, the engine warning lamp
(check engine lamp) illuminates as a
warning to the driver.
When an abnormality is detected in one
of the sensors or actuators, a diagnosiscode corresponding to the abnormality is
output.
The RAM data inside the ENGINE-ECU
that is related to the sensors and actuators
can be read by means of the MUT-II. In
addition, the actuators can be force-driven
under certain circumstances.