1993 CHEVROLET PLYMOUTH ACCLAIM ignition

WARNING: FUEL FILLER TUBE CAPS DESIGNED
FOR GASOLINE ONLY VEHICLES CANNOT BE
USED ON FLEXIBLE FUEL AA-BODY VEHICLES.
WHEN SERVICING THE FUEL SYSTEM OF A FLEX-
IBLE FUEL VEHICLE, ONLY USE ORIGINAL EQUIP-
MENT OR EQUIVALENT REPLACEMENT
COMPONENTS.
FUEL SYSTEM PRESSURE RELEASE
PROCEDUREÐEXCEPT 2.2L/2.5L TBI AND 3.0L
WARNING: RELEASE FUEL SYSTEM PRESSURE
BEFORE SERVICING FUEL SYSTEM COMPONENTS.
WHEN SERVICING FLEXIBLE FUEL VEHICLES,
WEAR METHANOL RESISTANT GLOVES AND EYE
PROTECTION AND AVOID BREATHING FUMES. DO
NOT ALLOW METHANOL/GASOLINE MIXTURES TO
CONTACT SKIN. SERVICE VEHICLES IN WELL VEN-
TILATED 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. 1).
(4) Place the open end of fuel pressure release
hose, tool number C-4799-1, into an approved gaso- line container or a container approved for methanol/
gasoline mixtures. Connect the other end of hose
C-4799-1 to the fuel pressure test port (Fig. 2). Fuel
pressure will bleed off through the hose into the gas-
oline container. Fuel gauge C-4799-A contains hose
C-4799-1.
FUEL SYSTEM PRESSURE RELEASE
PROCEDUREÐ2.2L/2.5L TBI
CAUTION: Before servicing the fuel pump, fuel
lines, fuel filter, throttle body, or fuel injector, re-
lease fuel system pressure.
(1) Loosen fuel filler cap to release fuel tank pres-
sure. (2) Disconnect injector wiring harness connector at
edge of throttle body (Fig. 3). (3) Connect a jumper wire between terminal Num-
ber 1 of the injector harness and engine ground. (4) Connect a jumper wire to the positive terminal
Number 2 of the injector harness and touch the bat-
tery positive post for no longer than 5 seconds .
This releases system pressure. (5) Remove jumper wires.
(6) Continue fuel system service.
FUEL SYSTEM PRESSURE RELEASE
PROCEDUREÐ3.0L
(1) Disconnect the fuel rail electrical harness from
the engine harness. Refer to Group 8W, Wiring Dia-
grams. (2) Connect one end of a jumper wire to the A142
circuit terminal of the fuel rail harness connector. (3) Connect the other end of the jumper wire to a
12 volt power source. (4) Connect one end of a jumper wire to a good
ground source. (5) Momentarily ground one of the injectors by
connecting the other end of the jumper wire to an in-
FUEL TANK CAPACITIES
Fig. 1 Fuel Pressure Test PortÐTypical
Fig. 2 Releasing Fuel PressureÐEngines With Test Ports On Fuel Rail
Ä FUEL SYSTEMS 14 - 15

jector terminal in the harness connector. Repeat pro-
cedure for 2 to 3 injectors.
FUEL TANK
DRAINING FUEL TANK
WARNING: RELEASE FUEL SYSTEM PRESSURE
BEFORE SERVICING FUEL SYSTEM COMPONENTS.
WHEN SERVICING FLEXIBLE FUEL VEHICLES,
WEAR METHANOL RESISTANT GLOVES AND EYE
PROTECTION AND AVOID BREATHING FUMES. DO
NOT ALLOW METHANOL/GASOLINE MIXTURES TO
CONTACT SKIN. SERVICE VEHICLES IN WELL VEN-
TILATED 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) Remove ground cable from battery.
(4) Raise vehicle on hoist.
(5) Remove rubber cap from drain tube. The tube
is located on rear of fuel tank. Connect either a por-
table holding tank or a siphon hose to the drain tube
(Fig. 4). (6) Drain fuel tank into holding tank or a properly
labeled Gasoline safety container.
FUEL TANK REMOVAL
WARNING: RELEASE FUEL SYSTEM PRESSURE
BEFORE SERVICING FUEL SYSTEM COMPONENTS.
WHEN SERVICING FLEXIBLE FUEL VEHICLES,
WEAR METHANOL RESISTANT GLOVES AND EYE
PROTECTION AND AVOID BREATHING FUMES. DO
NOT ALLOW METHANOL/GASOLINE MIXTURES TO
CONTACT SKIN. SERVICE VEHICLES IN WELL VEN-
TILATED AREAS AND AVOID IGNITION SOURCES.
NEVER SMOKE WHILE SERVICING THE VEHICLE.
(1) Perform fuel system pressure release.
(2) Drain fuel tank. Refer to Draining Fuel Tank
in this section. (3) Remove fuel filler tube to quarter panel screws
(Fig. 5). (4) Raise vehicle on hoist. Some models will re-
quire removal of the right rear wheel to access the
fuel filler tube.
WARNING: WRAP SHOP TOWELS AROUND HOSES
TO CATCH ANY GASOLINE SPILLAGE.
(5) Disconnect fuel pump and gauge sending unit
electrical connectors. (6) Disconnect the fuel supply and return hoses
from fuel pump. Refer to Quick Connect Hoses in the
Fuel Delivery section of this group. (7) Support tank with transmission jack. Loosen
tank mounting straps and lower tank slightly. Re-
move hose from pressure relief/rollover valve. (8) Carefully work fuel filler tube from tank.
(9) Remove tank mounting straps and lower tank.
(10) If removing tank from an flexible fuel AA-
body vehicle, inspect the heat shield. Replace as nec-
essary.
Fig. 3 Injector Harness ConnectorÐ2.2L/2.5L TBIFig. 4 Drain Tube Connection Location
14 - 16 FUEL SYSTEMS Ä

INSTALLATION
WARNING: FUEL TANKS DESIGNED FOR GASO-
LINE ONLY VEHICLES CANNOT BE USED ON
FLEXIBLE FUEL AA-BODY VEHICLES. WHEN SER-
VICING THE FUEL SYSTEM OF A FLEXIBLE FUEL
VEHICLE, ONLY USE ORIGINAL EQUIPMENT OR
EQUIVALENT REPLACEMENT COMPONENTS. (1) Position fuel tank on transmission jack. Con-
nect vapor separator/rollover valve hose and position
insulator pad on fuel tank. Position vapor vent so
that it is not pinched between tank and floor pan
during installation. (2) Raise tank and fuel filler tube carefully into
position. Use a light coating of power steering fluid
to ease fuel filler tube installation. Ensure filler tube
grommet is not damaged. Verify that the tube is in-
stalled correctly. (3) Tighten fuel tank strap nuts to 23 N Im (250 in.
lbs.) torque. Remove transmission jack. Ensure
straps are not twisted or bent. (4) Lubricate the metal tubes on the fuel pump
with clean 30 weight engine oil. Install the quick
connect fuel fittings. Refer to Quick Connect Fittings
in the Fuel Delivery section of this Group. (5) Attach electrical connector to fuel pump mod-
ule and level sensor unit. (6) Lower the vehicle.
(7) Attach filler tube to filler neck opening in
quarter panel. Tighten quarter panel screws to 2
N Im (17 in. lbs.) torque.
(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 un-
til the ignition switch is turned to the Off position.
(9) Use the DRBII scan tool ASD Fuel System Test
to pressurize the fuel system. Check for leaks.
FUEL PUMP MODULE
Refer to the Fuel Delivery section of this group.
METHANOL CONCENTRATION SENSOR
Refer to the Fuel Delivery section of this group.
FUEL RESERVOIR
The fuel reservoir is internal to the fuel pump as-
sembly (Fig. 6). The purpose is to provide fuel at the
fuel pump intake during all driving conditions, espe-
cially when low fuel levels are present.
FUEL TANK LEVEL SENSOR
DIAGNOSIS
This procedure test the resistance of the level sen-
sor itself. It does not test the level sensor circuit. Re-
fer to Group 8W, Wiring Diagrams for circuit
identification and Group 8E, Instrument Panel and
Gauges for fuel gauge information. 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 level sensor connector
(Fig. 7 or Fig. 8). Move the float lever to the full stop
and empty stop positions shown in the resistance
chart (Fig. 7 or Fig. 8). Record the resistance at each
point. Replace the level sensor if the resistance is not
within specifications. The low fuel warning light specifications determine
if the level sensor portion of the warning light circuit
functions properly. It does not test the complete
warning light circuit. Refer to Group 8W, Wiring Diagrams for circuit
identification and Group 8E, Instrument Panel and
Gauges for fuel gauge information.
REMOVAL
WARNING: RELEASE FUEL SYSTEM PRESSURE
BEFORE SERVICING FUEL SYSTEM COMPONENTS.
WHEN SERVICING FLEXIBLE FUEL VEHICLES,
WEAR METHANOL RESISTANT GLOVES AND EYE
PROTECTION AND AVOID BREATHING FUMES. DO
NOT ALLOW METHANOL/GASOLINE MIXTURES TO
CONTACT SKIN. SERVICE VEHICLES IN WELL VEN-
TILATED AREAS AND AVOID IGNITION SOURCES.
NEVER SMOKE WHILE SERVICING THE VEHICLE.
Fig. 6 Fuel Reservoir
14 - 18 FUEL SYSTEMS Ä

FUEL TANK PRESSURE RELIEF AND ROLL-OVER
VALVE
REMOVAL
WARNING: RELEASE FUEL SYSTEM PRESSURE BE-
FORE SERVICING FUEL SYSTEM COMPONENTS.
WHEN SERVICING FLEXIBLE FUEL VEHICLES,
WEAR METHANOL RESISTANT GLOVES AND EYE
PROTECTION AND AVOID BREATHING FUMES. DO
NOT ALLOW METHANOL/GASOLINE MIXTURES TO
CONTACT SKIN. SERVICE VEHICLES IN WELL VEN-
TILATED AREAS AND AVOID IGNITION SOURCES.
NEVER SMOKE WHILE SERVICING THE VEHICLE.
(1) Remove fuel tank. Refer to Fuel Tank Removal in
this section. (2) Wedge the blade of a screwdriver between the
rubber grommet and the fuel tank where the support
rib is located (Fig. 12). Do not wedge between the
valve and the grommet. This could damage the
valve during removal.
(3) Use a second screwdriver as a support to pry the
valve and grommet assembly from the tank. (4) Place the valve upright on a flat surface. Push
down on the grommet and peel it off the valve.
Fig. 9 Level Sensor RemovalÐTypical
Fig. 10 Fuel Tank Level SensorÐExcept Flexible Fuel AA-Body
Fig. 11 Fuel Tank Level SensorÐFlexible Fuel AA-Body
Fig. 12 Removing Pressure Relief/Rollover Valve
14 - 20 FUEL SYSTEMS Ä

2.2L/2.5L SINGLE POINT FUEL INJECTIONÐSYSTEM OPERATION INDEX
page page
Air Conditioning (A/C) Clutch RelayÐPCM Output.28
Air Conditioning Switch SenseÐPCM Input ..... 26
Auto Shutdown (ASD) Relay and Fuel Pump RelayÐPCM Output ..................... 29
Battery VoltageÐPCM Input ................ 26
Brake SwitchÐPCM Input .................. 26
EVAP Canister Purge SolenoidÐPCM Output . . . 29
CCD Bus .............................. 25
Coolant Temperature SensorÐPCM Input ...... 26
Data Link ConnectorÐPCM Output ........... 30
Distributor (Hall Effect) Pick-UpÐPCM Input .... 26
Electric Electronic Gas RecirculationÐPCM Output.30
Fuel InjectorÐPCM Output ................. 31
Fuel Pressure Regulator ................... 33
General Information ....................... 24
Generator FieldÐPCM Output ............... 31
Heated Oxygen Sensor (O
2Sensor)ÐPCM Input . 27
Idle Air Control MotorÐPCM Output .......... 29 Ignition CoilÐPCM Output
.................. 31
Malfunction Indicator Lamp (Check Engine)ÐPCM Output ............................... 30
Manifold Absolute Pressure (MAP) SensorÐPCM Input ................................ 27
Modes of Operation ....................... 32
Part Throttle Unlock SolenoidÐPCM Output .... 31
Powertrain Control Module ................. 25
Radiator Fan RelayÐPCM Output ............ 31
Speed Control SolenoidsÐPCM Output ........ 31
Speed ControlÐPCM Input ................. 27
System Diagnosis ........................ 25
TachometerÐPCM Output .................. 32
Throttle Body ............................ 33
Throttle Position Sensor (TPS)ÐPCM Input ..... 28
Transaxle Park/Neutral SwitchÐPCM Input ..... 28
Vehicle Speed SensorÐPCM Input ........... 28
GENERAL INFORMATION
The computer regulated, Electronic Fuel Injection
System (Fig. 1) provides a precise air/fuel ratio for
all driving conditions. The fuel injection system is
controlled by the powertrain control module (PCM).
The PCM is a pre-programmed digital computer. The
PCM regulates ignition timing, air-fuel ratio, emission
control devices, cooling fan, charging system, speed con-
trol, and idle speed. The PCM can adapt its requirement
to meet changing operating conditions.
Fig. 1 Electronic Fuel Injection Components
14 - 24 FUEL SYSTEMS Ä

Various sensors provide the inputs necessary for
the PCM to correctly regulate fuel flow at the fuel
injector. These include the manifold absolute pres-
sure, throttle position, oxygen sensor, coolant tem-
perature, and vehicle speed sensors. In addition to
the sensors, various switches and relays provide im-
portant information and system control. The inputs
include the park/neutral switch and air conditioning
clutch switch. The outputs include the auto shutdown
relay and fuel pump relay. All inputs to the PCM are converted into signals.
Based on these inputs the PCM adjusts air-fuel ratio,
ignition timing and other controlled outputs. The
PCM adjusts the air-fuel ratio by changing the injec-
tor pulse width. Injector pulse width is the period of
time the injector is energized.
SYSTEM DIAGNOSIS
The PCM tests many of its own input and output
circuits. If a fault is found in a major system, the in-
formation is stored in memory. Technicians can dis-
play fault information through the instrument panel
Malfunction Indicator lamp (instrument panel Check
Engine lamp) or by connecting the DRBII scan tool.
For diagnostic trouble code information, refer to On
Board Diagnostics in 2.2L/2.5L Single Point Fuel In-
jectionÐGeneral Diagnosis section of this group.
CCD BUS
Various modules exchange information through a
communications port called the CCD Bus. The pow-
ertrain control module (PCM) transmits vehicle load
data on the CCD Bus.
POWERTRAIN CONTROL MODULE
The powertrain control module (PCM) is a digital
computer containing a microprocessor (Fig. 2). The
PCM receives input signals from various switches
and sensors that are referred to as PCM Inputs.
Based on these inputs, the PCM adjusts various en-
gine and vehicle operations through devices that are
referred to as PCM Outputs. PCM Inputs:
² Air Conditioning Controls
² Battery Voltage
² Brake Switch
² Coolant Temperature Sensor
² Distributor (Hall Effect) Pick-up
² Manifold Absolute Pressure (MAP) Sensor
² Oxygen Sensor
² SCI Receive
² Speed Control System Controls
² Throttle Position Sensor
² Park/Neutral Switch (automatic transaxle)
² Vehicle Speed Sensor
PCM Outputs:
² Air Conditioning Clutch Relay
² Generator Field ²
Idle Air Control Motor
² Auto Shutdown (ASD) Relay
² Canister Purge Solenoid
² Malfunction Indicator (Check Engine) Lamp
² Data Link Connector (Diagnostic Connector)
² Electronic EGR Transducer
² Fuel Injector
² Ignition Coil
² Part Throttle Unlock Solenoid (Automatic Tran-
saxle)
² Radiator Fan Relay
² Speed Control Solenoids
² Tachometer Output
Based on inputs it receives, the PCM adjusts fuel
injector pulse width, idle speed, ignition spark ad-
vance, ignition coil dwell and canister purge opera-
tion. The PCM regulates operation of the EGR,
cooling fan, A/C and speed control systems. The PCM
changes generator charge rate by adjusting the gen-
erator field. The PCM adjusts injector pulse width (air-fuel ra-
tio) based on the following inputs.
² battery voltage
² coolant temperature
² exhaust gas content
² engine speed (distributor pick-up)
² manifold absolute pressure
² throttle position
The PCM adjusts ignition timing based on the fol-
lowing inputs.
² coolant temperature
² engine speed (distributor pick-up)
² manifold absolute pressure
² throttle position
The Auto Shutdown (ASD) and Fuel Pump relays
are mounted externally, but turned on and off by the
PCM through the same circuit. The distributor pick-up signal is sent to the PCM.
If the PCM does not receive a distributor signal
within approximately one second of engine cranking,
Fig. 2 PCM
Ä FUEL SYSTEMS 14 - 25

it de-activates the ASD relay and fuel pump relay.
When these relays are deactivated, power is shut off
from the fuel injector, fuel pump, ignition coil, and
oxygen sensor heater element. The PCM contains a voltage converter that
changes battery voltage to a regulated 8.0 volts to
power the distributor pick-up and vehicle speed sen-
sor. The PCM also provides a 5.0 volts supply for the
coolant temperature sensor, manifold absolute pres-
sure sensor and throttle position sensor.
AIR CONDITIONING SWITCH SENSEÐPCM INPUT
ALL VEHICLES EXCEPT AC-BODY
When the air conditioning or defrost switch is put
in the ON position and the low pressure and high
pressure switches are closed, the PCM receives an in-
put indicating that the air conditioning has been se-
lected. After receiving this input, the PCM activates
the A/C compressor clutch by grounding the A/C
clutch relay. The PCM also adjusts idle speed to a
scheduled RPM to compensate for increased engine
load.
AC-BODY VEHICLES
When the air conditioning or defrost switch is put
in the ON position and the low pressure switch, high
pressure switch and electronic cycling switch close,
the PCM receives an air conditioning select input.
After receiving this input, the PCM activates the
A/C compressor clutch by grounding the A/C com-
pressor clutch relay. The PCM also adjusts idle speed
to a scheduled RPM to compensate for increased en-
gine load.
BATTERY VOLTAGEÐPCM INPUT
The PCM monitors the battery voltage input to de-
termine fuel injector pulse width and generator field
control. If battery voltage is low, the PCM increases
injector pulse width.
BRAKE SWITCHÐPCM INPUT
When the brake switch is activated, the PCM re-
ceives an input indicating that the brakes are being
applied. After receiving the input, the PCM vents the
speed control servo. Venting the servo turns the
speed control system off.
COOLANT TEMPERATURE SENSORÐPCM INPUT
The coolant temperature sensor is installed behind
the thermostat housing and ignition coil in the hot
box. The sensor provides an input voltage to the
PCM (Fig. 3). As coolant temperature varies, the sen-
sors resistance changes, resulting in a different input
voltage to the PCM. The PCM demands slightly richer air-fuel mixtures
and higher idle speeds until the engine reaches nor-
mal operating temperature. This sensor is also used for cooling fan control.
DISTRIBUTOR (HALL EFFECT) PICK-UPÐPCM
INPUT
The distributor pick-up supplies engine speed to
the PCM. The distributor pick-up is a Hall Effect de-
vice (Fig. 4).
A shutter (sometimes referred to as an interrupter)
is attached to the distributor shaft. The shutter con-
tains four blades, one per engine cylinder. A switch
plate is mounted to the distributor housing above the
Fig. 3 Coolant Temperature Sensor
Fig. 4 Distributor Pick-UpÐTypical
14 - 26 FUEL SYSTEMS Ä

TRANSAXLE PARK/NEUTRAL SWITCHÐPCM
INPUT
The park/neutral switch is located on the auto-
matic transaxle housing (Fig. 7). Manual transaxles
do not use park neutral switches. The switch pro-
vides an input to the PCM. The input indicates
whether the automatic transaxle is in Park, Neutral,
or a drive gear selection. This input is used to deter-
mine idle speed (varying with gear selection), fuel in-
jector pulse width, and ignition timing advance. The
park neutral switch is sometimes referred to as the
neutral safety switch.
THROTTLE POSITION SENSOR (TPS)ÐPCM INPUT
The Throttle Position Sensor (TPS) is mounted on
the throttle body and connected to the throttle blade
shaft (Fig. 8). The TPS is a variable resistor. The
sensor provides an input signal (voltage) to the PCM
representing throttle blade position. As the position
of the throttle blade changes, the resistance of the
TPS changes.
The PCM supplies approximately 5 volts to the
TPS. The TPS output voltage (input signal to the
PCM) represents the throttle blade position. The
PCM receives an input signal voltage from the TPS
varying in an approximate range of from 1 volt at
minimum throttle opening (idle) to 4 volts at wide open throttle. Along with inputs from other sensors,
the PCM uses the TPS input to determine current
engine operating conditions. The PCM adjusts fuel
injector pulse width and ignition timing based on
these inputs.
VEHICLE SPEED SENSORÐPCM INPUT
The vehicle speed sensor is located in the transaxle
extension housing (Fig. 9). The sensor input is used
by the PCM to determine vehicle speed and distance
traveled.
The speed sensor generates 8 pulses per sensor rev-
olution. These signals, along with a closed throttle
signal from the TPS, determine if a closed throttle
deceleration or normal idle condition (vehicle
stopped) exists. Under deceleration conditions, the
PCM adjusts the idle air control motor to maintain a
desired MAP value. Under idle conditions, the PCM
adjusts the idle air control motor to maintain a de-
sired engine speed.
AIR CONDITIONING (A/C) CLUTCH RELAYÐPCM
OUTPUT
The PCM operates the air conditioning clutch relay
ground circuit. The radiator fan relay supplies bat-
tery power to the solenoid side of the A/C clutch re-
lay. The air conditioning clutch relay will not
energize unless the radiator fan relay energizes. The
PCM energizes the radiator fan relay when the air
conditioning or defrost switch is put in the ON posi-
tion and the low pressure and high pressure switches
close. With the engine operating, the PCM cycles the air
conditioning clutch on and off when the A/C switch
closes with the blower motor switch in the on posi-
tion. When the PCM senses low idle speeds or wide
open throttle through the throttle position sensor, it
de-energizes the A/C clutch relay. The relay contacts
open, preventing air conditioning clutch engagement.
Fig. 7 Park/Neutral Switch
Fig. 8 Throttle Position Sensor
Fig. 9 Vehicle Distance (Speed) SensorÐTypical
14 - 28 FUEL SYSTEMS Ä