fuel pressure DODGE NEON 1999 Service Service Manual

DIAGNOSIS AND TESTING
FUEL PUMP PRESSURE TEST
The fuel system operates at approximately 338 kPa
(49 psi). Check fuel system pressure at the test port
on the fuel rail (Fig. 7).
(1) Remove cap from fuel pressure test port on fuel
rail.
(2) Connect Fuel Pressure Gauge C-4799B to test
port (Fig. 8).CAUTION: When using the ASD Fuel System Test,
the ASD relay and fuel pump relay remain energized
for 7 minutes or until the test is stopped, or until
the ignition switch is turned to the Off position.
(3) Place the ignition key in the ON position.
Using the DRB scan tool, access ASD Fuel System
Test. The ASD Fuel System Test will activate the fuel
pump and pressurize the system.
²If the gauge reading equals 338 kPa (49 PSI)
further testing is not required. If pressure is not cor-
rect, record the pressure.
²If fuel pressure is below specifications, refer to
the Fuel Pressure Diagnosis Chart (Fig. 9).
²If fuel pressure is above specifications (54 psi or
higher) check for a kinked or restricted fuel supply
line. If the supply line is not kinked or restricted,
replace the Fuel Filter/Pressure Regulator.
(4) Replace Pressure test port cap when finished
doing pressure test.
FUEL LEVEL SENSOR
This procedure tests the resistance of the level sen-
sor itself. It does not test the level sensor circuit.
Refer to Group 8W - Wiring Diagrams for circuit
identification.
The level sensor is a variable resistor. Its resis-
tance changes with the amount of fuel in the tank.
The float arm attached to the sensor moves as the
fuel level changes. To test the level sensor, connect
an ohmmeter across the sensor signal and sensor
ground terminals of the fuel pump module connector
(Fig. 10). Move the float lever to the positions shown
in the resistance chart (Fig. 10). Record the resis-
tance at each point. Replace the level sensor if the
resistance is not within specifications.
Fig. 8 Checking Fuel Pressure at Intake ManifoldÐ
Typical
Fig. 6 Plastic Quick-Connect Fittings
Fig. 7 Fuel Pressure Test PortÐTypical
14 - 6 FUEL SYSTEMPL
DESCRIPTION AND OPERATION (Continued)

Fig. 9 Fuel Pressure Diagnosis Chart
PLFUEL SYSTEM 14 - 7
DIAGNOSIS AND TESTING (Continued)

SERVICE PROCEDURES
FUEL SYSTEM PRESSURE RELEASE PROCEDURE
WARNING: RELEASE FUEL SYSTEM PRESSURE
BEFORE SERVICING FUEL SYSTEM COMPONENTS.
SERVICE VEHICLES IN WELL VENTILATED AREAS
AND AVOID IGNITION SOURCES. NEVER SMOKE
WHILE SERVICING THE VEHICLE.
(1) Disconnect negative cable from battery.
(2) Remove fuel filler cap.
(3) Remove the protective cap from the fuel pres-
sure test port on the fuel rail (Fig. 11).
(4) Place the open end of fuel pressure release
hose, tool number C-4799-1, into an approved gaso-
line container. Connect the other end of hose
C-4799-1 to the fuel pressure test port (Fig. 12). Fuel
pressure will bleed off through the hose into the gas-
oline container. Fuel gauge C-4799-A contains hose
C-4799-1.
(5) Replace Pressure test port cap when finished
doing pressure test.
DRAINING FUEL TANK
WARNING: RELEASE FUEL SYSTEM PRESSURE
BEFORE SERVICING FUEL SYSTEM COMPONENTS.
SERVICE VEHICLES IN WELL VENTILATED AREAS
AND AVOID IGNITION SOURCES. NEVER SMOKE
WHILE SERVICING THE VEHICLE.
(1) Remove fuel filler cap.
(2) Perform the Fuel System Pressure Release pro-
cedure.
(3) Disconnect negative cable from battery.
(4) Raise vehicle on hoist.(5) Remove quick connect cap from drain port. The
drain port is located on rear top of fuel tank. Push a
siphon hose into the drain port (Fig. 13).
(6) Drain fuel tank into holding tank or a properly
labeledGasolinesafety container.
HOSES AND CLAMPS
Inspect all hose connections (clamps and quick con-
nect fittings) for completeness and leaks. Replace
cracked, scuffed, or swelled hoses. Replace hoses that
rub against other vehicle components or show sign of
wear.
Fuel injected vehicles use specially constructed
hoses. When replacing hoses, only use hoses marked
EFM/EFI.
When installing hoses, ensure that they are routed
away from contact with other vehicle components
that could rub against them and cause failure. Avoid
contact with clamps or other components that cause
abrasions or scuffing. Ensure that rubber hoses are
properly routed and avoid heat sources.
Fig. 11 Fuel Pressure Test PortÐTypical
Fig. 12 Releasing Fuel Pressure
Fig. 13 Drain Port Location
14 - 10 FUEL SYSTEMPL

The hose clamps have rolled edges to prevent the
clamp from cutting into the hose. Only use clamps
that are original equipment or equivalent. Other
types of clamps may cut into the hoses and cause
high pressure fuel leaks. Tighten hose clamps to 1
N´m (10 in. lbs.) torque.
QUICK-CONNECT FITTINGS
REMOVAL
When disconnecting a quick-connect fitting, the
retainer will remain on the fuel tube nipple.
WARNING: RELEASE FUEL SYSTEM PRESSURE
BEFORE DISCONNECTING A QUICK-CONNECT FIT-
TINGS. REFER TO THE FUEL PRESSURE RELEASE
PROCEDURE.
(1) Disconnect negative cable from battery.
(2) Perform Fuel Pressure Release Procedure.
Refer to the Fuel Pressure Release Procedure in this
section.
(3) Squeeze retainer tabs together and pull fuel
tube/quick-connect fitting assembly off of fuel tube
nipple. The retainer will remain on fuel tube.
INSTALLATION
CAUTION: Never install a quick-connect fitting
without the retainer being either on the fuel tube or
already in the quick-connect fitting. In either case,
ensure the retainer locks securely into the quick-
connect fitting by firmly pulling on fuel tube and fit-
ting to ensure it is secured.
(1) Using a clean lint free cloth, clean the fuel tube
nipple and retainer.
(2) Prior to connecting the fitting to the fuel tube,
coat the fuel tube nipple with clean 30 weight engine
oil.
(3) Push the quick-connect fitting over the fuel
tube until theretainer seats and a click is heard.
(4) The plastic quick-connect fitting has windows
in the sides of the casing. When the fitting com-
pletely attaches to the fuel tube, the retainer locking
ears and the fuel tube shoulder are visible in the
windows. If they are not visible, the retainer was not
properly installed (Fig. 14).Do not rely upon the
audible click to confirm a secure connection.
CAUTION: When using the ASD Fuel System Test,
the Auto Shutdown (ASD) Relay remains energized
for either 7 minutes, until the test is stopped, or
until the ignition switch is turned to the Off posi-
tion.
(5) Use the DRB scan tool ASD Fuel System Test
to pressurize the fuel system. Check for leaks.
REMOVAL AND INSTALLATION
AUTOMATIC SHUTDOWN RELAY
The relay is located in the Power Distribution Cen-
ter (PDC) (Fig. 15). The PDC is located next to the
battery in the engine compartment. For the location
of the relay within the PDC, refer to the PDC cover
for location. Check electrical terminals for corrosion
and repair as necessary.
FUEL PUMP RELAY
The fuel pump relay is located in the PDC. The
inside top of the PDC cover has a label showing relay
and fuse location.
FUEL PUMP MODULE
REMOVAL
WARNING: RELEASE FUEL SYSTEM PRESSURE
BEFORE SERVICING FUEL SYSTEM COMPONENTS.
SERVICE VEHICLES IN WELL VENTILATED AREAS
AND AVOID IGNITION SOURCES. NEVER SMOKE
WHILE SERVICING THE VEHICLE.
(1) Drain the fuel. Refer to Draining Fuel Tank in
the Fuel Tank section of this group.
Fig. 14 Plastic Quick-Connect Fitting/Fuel Tube
Connection
Fig. 15 Power Distribution Center (PDC)
PLFUEL SYSTEM 14 - 11
SERVICE PROCEDURES (Continued)

WARNING: THE FUEL RESERVOIR OF THE FUEL
PUMP MODULE DOES NOT EMPTY OUT WHEN THE
TANK IS DRAINED. THE FUEL IN THE RESERVOIR
WILL SPILL OUT WHEN THE MODULE IS
REMOVED.
(2) Disconnect fuel line from fuel pump module by
depressing quick connect retainers with thumb and
fore finger.
(3) Slide fuel pump module electrical connecter
lock to unlock.
(4) Disconnect the electrical connection from the
fuel pump module, by pushing down on connector
retainer and pulling connector off of module.
(5) Use a transmission jack to support the fuel
tank. remove bolts from fuel tank straps.
(6) Lower tank slightly.
(7) Use Special Tool 6856 to remove fuel pump
module locknut (Fig. 17).
(8) Remove fuel pump and O-ring seal from tank.
Discard old seal.
INSTALLATION
(1) Wipe seal area of tank clean and place a new
seal in position in the tank opening.
(2) Position fuel pump in the tank. Make sure the
aligment tab on the underside of the fuel pump mod-
ule flange sits in the notch on the fuel tank.
(3)
Position the locknut over the fuel pump module.
(4) Tighten the locknut using Special Tool 6856 to
55 N´m (40.5 ft. lbs.) (Fig. 17).
CAUTION: Over tightening the pump lock ring may
result in a leak.
(5) Fill fuel tank. Check for leaks.
FUEL FILTER / PRESSURE REGULATOR
REMOVAL
WARNING: THE FUEL SYSTEM IS UNDER A CON-
STANT PRESSURE, EVEN WITH ENGINE OFF. BEFORE
SERVICING THE FUEL FILTER/FUEL PRESSURE REG-
ULATOR, THE FUEL SYSTEM PRESSURE MUST BE
RELEASED.
(1) Refer to Fuel System Pressure Release in the
Fuel Delivery System section of this group.
The fuel filter/fuel pressure regulator is located on
the top of fuel pump module. Fuel pump module
removal is not necessary.
(2) Raise vehicle on hoist.
(3) Disconnect fuel supply line at the Filter/Regu-
lator nipple (refer to Quick Connect Fittings in this
section).
(4) Depress locking spring tab on side of Fuel/Reg-
ulator (Fig. 18) and rotate 90É counter-clockwise and
pull out.
NOTE: Make sure that the upper and lower O-rings
are on the Filter/Regulator assembly.
INSTALLATION
Lightly lubricate the O-rings with engine oil.
(1) Insert Filter/Regulator into the opening in the
fuel pump module, align the two hold down tabs with
the flange.
(2) While applying downward pressure, rotate the
Filter/Regulator clockwise until the the spring tab
engages the locating slot (Fig. 19).
(3) Connect the fuel line to the Filter/Regulator.
(4) Lower vehicle from hoist.
Fig. 16 Fuel Pump Module Removal
Fig. 17 Fuel Tank Locknut
14 - 12 FUEL SYSTEMPL
REMOVAL AND INSTALLATION (Continued)

(6) Slide level sensor wires through opening fuel
pump module (Fig. 26).
(7) Slide level sensor out of installation channel in
module.
INSTALLATION
(1) Insert level sensor wires into bottom of opening
in module.
(2) Wrap wires into groove in back of level sensor
(Fig. 25).
(3) While feeding wires into guide grooves, slide
level sensor up into channel until it snaps into place
(Fig. 26). Ensure tab at bottom of sensor locks in
place.(4) Install level sensor wires in connector. Push
the wires up through the connector and then pull
them down until they lock in place. Ensure signal
and ground wires are installed in the correct posi-
tion.
(5) Install locking wedge on connector.
(6) Push connector up into bottom of fuel pump
module electrical connector.
(7) Install fuel pump module. Refer to Fuel Pump
Module in this section.
FUEL INJECTORS
REMOVAL
(1) Disconnect negative cable from battery.
(2) Release fuel system pressure. Refer to Fuel
System Pressure Release procedure in this section.
(3) Disconnect fuel supply tube from rail. Refer to
Quick-Connect Fittings in the Fuel Delivery section
of this group.
(4) Disconnect electrical connectors from fuel injec-
tors (Fig. 27).
Fig. 22 Wire Terminal Locking Wedge
Fig. 23 Wire Terminal Locking Finger
Fig. 24 Removing Wires From Connector
Fig. 25 Loosening Level Sensor
Fig. 26 Level Sensor Removal/Installation
14 - 14 FUEL SYSTEMPL
REMOVAL AND INSTALLATION (Continued)

(5) Remove fuel rail mounting screws.
(6) Lift rail off of intake manifold. Cover the fuel
injector openings in the intake manifold.
(7) Remove fuel injector retainer (Fig. 28).
(8) Pull injector out of fuel rail. Replace fuel injec-
tor O-rings (Fig. 29).
INSTALLATION
(1) Apply a light coating of clean engine oil to the
upper O-ring.(2) Install injector in cup on fuel rail.
(3) Install retaining clip.
(4) Apply a light coating of clean engine oil to the
O-ring on the nozzle end of each injector.
(5) Insert fuel injector nozzles into openings in
intake manifold. Seat the injectors in place. Tighten
fuel rail mounting screws to 22.5 N´m63 N´m
(200630 in. lbs.).
(6) Attach electrical connectors to fuel injectors.
(7) Connect fuel supply tube to fuel rail. Refer to
Quick Connect Fittings in the Fuel Delivery Section
of this Group.
FUEL TANK
REMOVAL
(1) Perform fuel system pressure release.
(2) Drain fuel tank. Refer to Draining Fuel Tank
in this section (Fig. 30).
(3) Raise vehicle on hoist.
WARNING: WRAP SHOP TOWELS AROUND
HOSES TO CATCH ANY GASOLINE SPILLAGE.
(4) Disconnect fuel pump module electrical connec-
tor (Fig. 31).
(5) Disconnect the fuel tube from Fuel Filter/Reg-
ulator. Refer to Quick Connect Fittings in the Fuel
Delivery section of this group.
(6) Support tank with transmission jack. Loosen
tank mounting straps and lower tank slightly.
(7) Disconnect fuel filler tube and filler vent tube
from filler hose at fuel tank (Fig. 32).
(8) Disconnect fuel filler vapor relief tube from tee
connecting it to the tank vapor relief tube and EVAP
canister tube.
(9) Disconnect vapor line from Evap canister tube.
(10) Remove tank mounting straps and lower tank.Fig. 27 Fuel Rail and Injectors
Fig. 28 Fuel Injector Retainer
Fig. 29 Fuel Injector O-Rings
Fig. 30 Fuel Tank
PLFUEL SYSTEM 14 - 15
REMOVAL AND INSTALLATION (Continued)

INSTALLATION
(1) Position fuel tank on transmission jack.
(2) Raise tank into position. Connect fuel filler
tube tank inlet nipple.
(3) Tighten fuel tank strap nuts to 22.5 N´m (200
in. lbs.) torque. Remove transmission jack. Ensure
straps are not twisted or bent.
(4) Attach fuel tubes to pump module and chassis
fuel tube. Refer to Quick Connect Fittings in the Fuel
Delivery section of this Group.
(5) Connect fuel vapor tube to tee, then to Evap
canister tube.
(6)
Attach electrical connector to fuel pump module.
(7) Lower vehicle.
(8) Fill fuel tank, install filler cap, and connect
battery cable.
CAUTION: When using the ASD Fuel System Test, the
Auto Shutdown (ASD) Relay remains energized for
either 7 minutes, until the test is stopped, or until the
ignition switch is turned to the Off position.
(9) Use the DRB scan tool ASD Fuel System Test
to pressurize the fuel system. Check for leaks.
FUEL FILLER NECK
REMOVAL
(1) Loosen fuel filler tube cap.
(2) Remove fuel filler neck screws (Fig. 33).
(3) Disconnect fuel fill vapor tube.
(4) Disconnect fuel filler tube from fuel tank.
Remove filler neck.
INSTALLATION
(1) Reverse for installation.
FUEL FILLER TUBE ROLLOVER VALVE
REMOVAL
The rollover valve is mounted in the fuel filler tube
(Fig. 34).
(1) To release fuel tank pressure, remove the fuel
filler tube cap.
Fig. 31 Fuel Pump Module Electrical Connector
Fig. 32 Fuel Filler Tube and Vent Tubes
Fig. 33 Fuel Filler Neck
Fig. 34 Fuel Filler Tube Rollover Valve
14 - 16 FUEL SYSTEMPL
REMOVAL AND INSTALLATION (Continued)

FUEL INJECTION SYSTEM
INDEX
page page
GENERAL INFORMATION
INTRODUCTION......................... 21
MODES OF OPERATION.................. 21
DESCRIPTION AND OPERATION
AIR CONDITIONING CLUTCH RELAYÐ
PCM OUTPUT......................... 31
AIR CONDITIONING PRESSURE
TRANSDUCERÐPCM INPUT............. 25
AUTOMATIC SHUTDOWN (ASD) SENSEÐ
PCM INPUT........................... 25
AUTOMATIC SHUTDOWN RELAYÐ
PCM OUTPUT......................... 32
BATTERY TEMPERATURE SENSORÐ
PCM INPUT........................... 25
BATTERY VOLTAGEÐPCM INPUT........... 25
BRAKE SWITCHÐPCM INPUT.............. 25
CAMSHAFT POSITION SENSORÐPCM INPUT . 25
CHARGING SYSTEM INDICATOR LAMPÐ
PCM OUTPUT......................... 32
CRANKSHAFT POSITION SENSORÐ
PCM INPUT........................... 26
DATA LINK CONNECTOR.................. 33
DUTY CYCLE EVAP PURGE SOLENOIDÐ
PCM OUTPUT......................... 32
ELECTRIC EGR TRANSDUCERÐ
PCM OUTPUT......................... 32
ENGINE COOLANT TEMPERATURE SENSORÐ
PCM INPUT........................... 26
FUEL INJECTORSÐPCM OUTPUT.......... 34
FUEL LEVEL SENSORÐPCM INPUT......... 27
FUEL PUMP RELAYÐPCM OUTPUT......... 32
GENERATOR FIELDÐPCM OUTPUT......... 33
HEATED OXYGEN SENSOR (O2S SENSOR)Ð
PCM INPUT........................... 27
IDLE AIR CONTROL MOTORÐPCM OUTPUT . . 33
IGNITION CIRCUIT SENSEÐPCM INPUT..... 28
IGNITION COILÐPCM OUTPUT............. 34
INTAKE AIR TEMPERATURE SENSORÐ
PCM INPUT........................... 28
KNOCK SENSORÐPCM INPUT............. 29
MALFUNCTION INDICATOR (CHECK ENGINE)
LAMPÐPCM OUTPUT.................. 34
MANIFOLD ABSOLUTE PRESSURE (MAP)
SENSORÐPCM INPUT.................. 29
PARK/NEUTRAL POSITION SWITCHÐ
PCM INPUT........................... 30
POWER DISTRIBUTION CENTER........... 23
POWER STEERING PRESSURE SWITCHÐ
PCM INPUT........................... 30
POWERTRAIN CONTROL MODULE.......... 24SCI RECEIVEÐPCM INPUT................ 30
SCI RECEIVEÐPCM OUTPUT.............. 35
SENSOR RETURNÐPCM INPUT............ 30
SOLID STATE FAN RELAYÐPCM OUTPUT.... 35
SPEED CONTROL SERVOSÐPCM OUTPUT . . . 30
SPEED CONTROLÐPCM INPUT............ 35
SYSTEM DIAGNOSIS..................... 23
TACHOMETERÐPCM OUTPUT............. 35
THROTTLE POSITION SENSORÐPCM INPUT . 30
TORQUE CONVERTOR CLUTCH SOLENOIDÐ
PCM OUTPUT......................... 35
VEHICLE SPEED SENSORÐPCM INPUT..... 30
DIAGNOSIS AND TESTING
ASD AND FUEL PUMP RELAYS............. 46
CAMSHAFT AND CRANKSHAFT POSITION
SENSOR............................. 47
ENGINE COOLANT TEMPERATURE SENSOR . . 47
HEATED OXYGEN SENSOR............... 47
IDLE AIR CONTROL (IAC) MOTOR TEST...... 47
KNOCK SENSOR........................ 47
MANIFOLD ABSOLUTE PRESSURE (MAP)
SENSOR............................. 48
THROTTLE BODY MINIMUM AIR FLOW....... 48
THROTTLE POSITION SENSOR............ 48
VEHICLE SPEED SENSOR................ 49
VISUAL INSPECTIONÐDOHC.............. 40
VISUAL INSPECTIONÐSOHC.............. 35
REMOVAL AND INSTALLATION
AIR CLEANER ELEMENT.................. 55
CAMSHAFT POSITION SENSOR............ 54
CRANKSHAFT POSITION SENSOR.......... 54
DOWNSTREAM HEATED OXYGEN SENSOR . . . 55
DUTY CYCLE EVAP PURGE SOLENOID VALVE . 53
ENGINE COOLANT TEMPERATURE SENSOR . . 56
IDLE AIR CONTROL MOTOR............... 52
KNOCK SENSOR........................ 57
MAP/IAT SENSORÐDOHC................. 53
MAP/IAT SENSORÐSOHC................. 53
POWERTRAIN CONTROL MODULE (PCM).... 54
THROTTLE BODYÐAUTOMATIC
TRANSMISSION....................... 50
THROTTLE BODYÐMANUAL TRANSMISSION . 50
THROTTLE POSITION SENSOR (TPS)....... 52
UPSTREAM HEATED OXYGEN SENSOR...... 54
VEHICLE SPEED SENSOR................ 56
SPECIFICATIONS
TORQUE.............................. 57
VECI LABEL............................ 57
SPECIAL TOOLS
FUEL................................. 57
14 - 20 FUEL SYSTEMPL

GENERAL INFORMATION
INTRODUCTION
All engines used in this section have a sequential
Multi-Port Electronic Fuel Injection system. The MPI
system is computer regulated and provides precise
air/fuel ratios for all driving conditions. The Power-
train Control Module (PCM) operates the fuel injec-
tion system.
The PCM regulates:
²Ignition timing
²Air/fuel ratio
²Emission control devices
²Cooling fan
²Charging system
²Idle speed
²Vehicle speed control
Various sensors provide the inputs necessary for
the PCM to correctly operate these systems. In addi-
tion to the sensors, various switches also provide
inputs to the PCM.
All inputs to the PCM are converted into signals.
The PCM can adapt its programming to meet chang-
ing operating conditions.
Fuel is injected into the intake port above the
intake valve in precise metered amounts through
electrically operated injectors. The PCM fires the
injectors in a specific sequence. Under most operat-
ing conditions, the PCM maintains an air fuel ratio
of 14.7 parts air to 1 part fuel by constantly adjust-
ing injector pulse width. Injector pulse width is the
length of time the injector is open.
The PCM adjusts injector pulse width by opening
and closing the ground path to the injector. Engine
RPM (speed) and manifold absolute pressure (air
density) are the primary inputs that determine injec-
tor pulse width.
MODES OF OPERATION
As input signals to the PCM change, the PCM
adjusts its response to output devices. For example,
the PCM must calculate a different injector pulse
width and ignition timing for idle than it does for
Wide Open Throttle (WOT). There are several differ-
ent modes of operation that determine how the PCM
responds to the various input signals.
There are two different areas of operation, OPEN
LOOP and CLOSED LOOP.
During OPEN LOOP modes the PCM receives
input signals and responds according to preset PCM
programming. Inputs from the upstream and down-
stream heated oxygen sensors are not monitored dur-
ing OPEN LOOP modes, except for heated oxygen
sensor diagnostics (they are checked for shorted con-
ditions at all times).During CLOSED LOOP modes the PCM monitors
the inputs from the upstream and downstream
heated oxygen sensors. The upstream heated oxygen
sensor input tells the PCM if the calculated injector
pulse width resulted in the ideal air-fuel ratio of 14.7
to one. By monitoring the exhaust oxygen content
through the upstream heated oxygen sensor, the
PCM can fine tune injector pulse width. Fine tuning
injector pulse width allows the PCM to achieve opti-
mum fuel economy combined with low emissions.
For the PCM to enter CLOSED LOOP operation,
the following must occur:
(1) Engine coolant temperature must be over 35ÉF.
²If the coolant is over 35É the PCM will wait 44
seconds.
²If the coolant is over 50ÉF the PCM will wait 38
seconds.
²If the coolant is over 167ÉF the PCM will wait
11 seconds.
(2) For other temperatures the PCM will interpo-
late the correct waiting time.
(3) O2 sensor must read either greater than .745
volts or less than .1 volt.
(4) The multi-port fuel injection systems has the
following modes of operation:
²Ignition switch ON (Zero RPM)
²Engine start-up
²Engine warm-up
²Cruise
²Idle
²Acceleration
²Deceleration
²Wide Open Throttle
²Ignition switch OFF
(5) The engine start-up (crank), engine warm-up,
deceleration with fuel shutoff and wide open throttle
modes are OPEN LOOP modes. Under most operat-
ing conditions, the acceleration, deceleration (with
A/C on), idle and cruise modes,with the engine at
operating temperatureare CLOSED LOOP modes.
IGNITION SWITCH ON (ZERO RPM) MODE
When the ignition switch activates the fuel injec-
tion system, the following actions occur:
²The PCM monitors the engine coolant tempera-
ture sensor and throttle position sensor input. The
PCM determines basic fuel injector pulse width from
this input.
²The PCM determines atmospheric air pressure
from the MAP sensor input to modify injector pulse
width.
When the key is in the ON position and the engine
is not running (zero rpm), the Auto Shutdown (ASD)
and fuel pump relays de-energize after approximately
1 second. Therefore, battery voltage is not supplied to
the fuel pump, ignition coil, fuel injectors and heated
oxygen sensors.
PLFUEL SYSTEM 14 - 21