Chrysler Le Baron, Dodge Dynasty, Plymouth Acclaim. Manual — part 59
IGNITION SWITCH ON (ZERO RPM) MODE
When the multi-port fuel injection system is acti-
vated by the ignition switch, the following actions oc-
cur:
• The PCM determines atmospheric air pressure
from the MAP sensor input to determine basic fuel
strategy.
• The PCM monitors the coolant temperature sensor
and throttle position sensor input. The PCM modifies
fuel strategy based on this input.
When the key is in the ON position and the engine
is not running (zero rpm), the auto shutdown (ASD)
relay and fuel pump relay are not energized. There-
fore battery voltage is not supplied to the fuel pump,
ignition coil, fuel injectors or oxygen sensor heating
element.
ENGINE START-UP MODE
This is an OPEN LOOP mode. The following ac-
tions occur when the starter motor is engaged.
If the PCM receives the camshaft position sensor
and crankshaft position sensor signals, it energizes
the auto shutdown (ASD) relay and fuel pump relay.
These relays supply battery voltage to the fuel pump,
fuel injectors, ignition coil, and oxygen sensor heat-
ing element. If the PCM does not receive the cam-
shaft position sensor and crankshaft position sensor
signals within approximately one second, it de-ener-
gizes the ASD relay and fuel pump relay.
The PCM energizes all six injectors until it deter-
mines crankshaft position from the camshaft position
sensor and crankshaft position sensor signals. The
PCM determines crankshaft position within 1 engine
revolution.
After determining crankshaft position, the PCM
begins energizing the injectors in sequence. The PCM
adjusts injector pulse width and controls injector syn-
chronization by turning the individual ground paths
to the injectors On and Off.
When the engine idles within
664 RPM of its tar-
get RPM, the PCM compares current MAP sensor
value with the atmospheric pressure value received
during the Ignition Switch On (Zero RPM) mode. If
the PCM does not detect a minimum difference be-
tween the two values, it sets a MAP fault into mem-
ory.
Once the ASD and fuel pump relays have been en-
ergized, the PCM:
• Determines injector pulse width based on battery
voltage, coolant temperature, engine rpm and the
number of engine revolutions since cranking was ini-
tiated.
ENGINE WARM-UP MODE
This is a OPEN LOOP mode. The following inputs
are received by the PCM:
• engine coolant temperature
• manifold absolute pressure (MAP)
• engine speed (crankshaft position sensor)
• throttle position
• A/C switch
• battery voltage
The PCM adjusts injector pulse width and controls
injector synchronization by turning the individual
ground paths to the injectors On and Off.
The PCM adjusts ignition timing and engine idle
speed. Engine idle speed is adjusted through the idle
air control motor.
CRUISE OR IDLE MODE
When the engine is at operating temperature this
is a CLOSED LOOP mode. During cruising speed the
following inputs are received by the PCM:
• engine coolant temperature
• manifold absolute pressure
• engine speed (crankshaft position sensor)
• throttle position
• exhaust gas oxygen content
• A/C control positions
• battery voltage
The PCM adjusts injector pulse width and controls
injector synchronization by turning the individual
ground paths to the injectors On and Off.
The PCM adjusts engine idle speed and ignition
timing. The PCM adjusts the air/fuel ratio according
to the oxygen content in the exhaust gas.
ACCELERATION MODE
This is a CLOSED LOOP mode. The PCM recog-
nizes an abrupt increase in throttle position or MAP
pressure as a demand for increased engine output
and vehicle acceleration. The PCM increases injector
pulse width in response to increased fuel demand.
DECELERATION MODE
This is a CLOSED LOOP mode. During decelera-
tion the following inputs are received by the PCM:
• engine coolant temperature
• manifold absolute pressure
• engine speed
• throttle position
• exhaust gas oxygen content
• A/C control positions
• battery voltage
The PCM may receive a closed throttle input from
the throttle position sensor (TPS) when it senses an
abrupt decrease in manifold pressure. This indicates
a hard deceleration. The PCM will reduce injector
pulse width. This helps maintain better control of the
air-fuel mixture (as sensed through the O
2
sensor).
During a closed throttle deceleration condition, the
PCM grounds the exhaust gas recirculation (EGR)
solenoid. When the solenoid is grounded, EGR func-
tion stops.
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FUEL SYSTEMS
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WIDE OPEN THROTTLE MODE
This is an OPEN LOOP mode. During wide-open-
throttle operation, the following inputs are received
by the PCM:
• battery voltage
• engine coolant temperature
• manifold absolute pressure
• engine speed
• throttle position
When the PCM senses wide open throttle condition
through the throttle position sensor (TPS) it will:
• De-energize the air conditioning relay. This dis-
ables the air conditioning system.
• Provide a ground for the electrical EGR transducer
(EET) solenoid. When the PCM grounds the solenoid,
the EGR system stops operating.
The exhaust gas oxygen content input is not ac-
cepted by the PCM during wide open throttle opera-
tion. The PCM will adjust injector pulse width to
supply a predetermined amount of additional fuel.
IGNITION SWITCH OFF MODE
When the ignition switch is turned to the OFF po-
sition, the following occurs:
• All outputs are turned off.
• No inputs are monitored.
• The PCM shuts down.
THROTTLE BODY
The throttle body assembly is located on the left
side of the intake manifold plenum (Fig. 19). The
throttle body houses the throttle position sensor and
the idle air control motor. Air flow through the throt-
tle body is controlled by a cable operated throttle
blade located in the base of the throttle body.
FUEL SUPPLY CIRCUIT
Fuel is pumped to the fuel rail by an electrical
pump in the fuel tank. The pump inlet is fitted with
a strainer to prevent water and other contaminants
from entering the fuel supply circuit.
Fuel pressure is controlled to a preset level above
intake manifold pressure by a pressure regulator.
The regulator is mounted on the fuel rail. The regu-
lator uses intake manifold pressure as a reference.
FUEL INJECTORS AND FUEL RAIL ASSEMBLY
Six fuel injectors are retained in the fuel rail by
lock rings (Fig. 20). The rail and injector assembly is
installed in position with the injectors inserted in re-
cessed holes in the intake manifold.
Fig. 19 Throttle Body
Fig. 20 Fuel Rail Assembly
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FUEL SYSTEMS
14 - 155
FUEL PRESSURE REGULATOR
The pressure regulator is a mechanical device lo-
cated on the fuel rail, downstream of the fuel injec-
tors (Fig. 21). The regulator maintains a constant
330 kPa (48 psi) across the fuel injector tip.
The regulator contains a spring loaded rubber dia-
phragm that covers the fuel return port. When the
fuel pump is operating, fuel flows past the injectors
into the regulator, and is restricted from flowing any
further by the blocked return port. When fuel pres-
sure reaches 330 kPa (48 psi) it pushes on the dia-
phragm, compresses the spring, and uncovers the
fuel return port. The diaphragm and spring con-
stantly move from an open to closed position keeping
fuel pressure consistent.
Fig. 21 Fuel Pressure Regulator
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FUEL SYSTEMS
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3.3L AND 3.8L MULTI-PORT FUEL INJECTION—GENERAL DIAGNOSIS
INDEX
page
page
Fuel System Diagram
. . . . . . . . . . . . . . . . . . . . 157
Visual Inspection
. . . . . . . . . . . . . . . . . . . . . . . . 157
FUEL SYSTEM DIAGRAM
Refer to the Component Identification portion of
this section for a more complete description of the
components shown in Fig. 1.
VISUAL INSPECTION
Perform a visual inspection for loose, disconnected,
or misrouted wires and hoses before diagnosing or
servicing the fuel injection system. A visual check
saves unnecessary test and diagnostic time. A thor-
ough visual inspection includes the following checks:
(1) Check ignition cable routing from the coil pack
to the spark plugs. Verify the cable are routed in the
correct order and are fully seated to the coil and
spark plug.
(2) Check direct ignition system (DIS) coil electri-
cal connection for damage and a complete connection
to the coil (Fig. 2).
(3) Verify the camshaft position sensor electrical
connector is connected to the harness and not dam-
aged (Fig. 3).
(4) Ensure the engine temperature sensor electri-
cal connector is connected to the sensor and not dam-
aged (Fig. 3).
(5) Ensure the coolant temperature sensor electri-
cal connector is connected to the sensor and not dam-
aged (Fig. 4).
(6) Verify the quick connect fuel fittings are fully
inserted on the fuel supply and return tubes.
(7) Check the vacuum hose connection at the fuel
pressure regulator for damage or leakage (Fig. 5).
(8) Check the oil pressure sending unit electrical
connection (Fig. 6).
(9) Verify the electrical connector is attached to
the Purge Solenoid (Fig. 7) and not damaged.
(10) Verify the vacuum connection at the purge so-
lenoid is secure and not leaking (Fig. 7).
Fig. 1 Multi-Port Fuel Injection Components
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FUEL SYSTEMS
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