key CHRYSLER VOYAGER 1996 Service Manual

(4) Install the fuel rail mounting bolts. Tighten
bolts to 22 N´m (200 in. lbs.) torque (Fig. 51).
(5) Install fuel tube retaining bracket screw.
Tighten screw to 4 N´m (35 in. lbs.) torque.
(6) Connect electrical connectors to camshaft posi-
tion sensor and engine coolant temperature sensor.
(7) Remove covering on lower intake manifold and
clean surface.
(8) Place intake manifold gasket on lower mani-
fold. Put upper manifold into place and install bolts
finger tight.
(9) Install the generator bracket to intake mani-
fold bolt and the cylinder head to intake manifold
strut bolts (do not tighten.)(10) Following the tightening sequence in (Fig. 50),
tighten intake manifold bolts to 28 N´m (250 in. lbs.)
torque.
(11) Tighten generator bracket to intake manifold
bolt to 54 N´m (40 ft. lbs.) torque.
(12) Tighten the cylinder head to intake manifold
strut bolts to 54 N´m (40 ft. lbs.) torque.
(13) Connect ground strap and MAP sensor electri-
cal connector.
(14) Connect vacuum harness to intake plenum.
Connect PCV system hoses.
(15) Using a new gasket, connect the EGR tube to
the intake manifold plenum. Tighten screws to 22
N´m (200 in. lbs.) torque.
(16) Connect electrical connectors to the TPS and
idle air control motor.
(17) Connect vacuum harness to throttle body.
(18) Install the direct ignition system (DIS) coils.
Tighten fasteners to 12 N´m (105 in. lbs.) torque.
(19) Install fuel hose quick connector fitting to
chassis tubes.Refer to Fuel Hoses, Clamps and
Quick Connect Fittings in this Section.Push the
fitting onto the chassis tube until it clicks into place.
Pull on the fitting to ensure complete insertion.
(20) Install throttle cable and speed control cable
(if equipped).
(21) Install air inlet resonator.
(22) Connect negative cable to battery.
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.
(23) With the ignition key in ON position, access
the DRB scan tool ASD Fuel System Test to pressur-
ize the fuel system. Check for leaks.
FUEL INJECTORÐ2.4L
The fuel rail must be removed first. Refer to Fuel
Injector Rail Removal in this section.
REMOVAL
(1) Disconnect injector wiring connector from injec-
tor.
(2) Position fuel rail assembly so that the fuel
injectors are easily accessible (Fig. 54).
(3) Rotate injector and pull injector out of fuel rail.
The clip will stay on the injector.
(4) Check injector O-ring for damage. If O-ring is
damaged, it must be replaced. If injector is reused, a
protective cap must be installed on the injector tip to
prevent damage. Replace the injector clip if it is dam-
aged.
(5) Repeat for remaining injectors.
Fig. 52 Camshaft Position Sensor Connector
Fig. 53 Fuel Rail Removal
14 - 24 FUEL SYSTEMNS
REMOVAL AND INSTALLATION (Continued)

INSTALLATION
(1) Before installing an injector the rubber O-ring
must be lubricated with a drop of clean engine oil to
aid in installation.
(2) Install injector clip by sliding open end into the
top slot of the injector. The edge of the receiver cup
will slide into the side slots of clip.
(3) Install injector top end into fuel rail receiver
cap. Be careful not to damage O-ring during installa-
tion (Fig. 55).
(4) Repeat steps for remaining injectors.
(5) Connect fuel injector wiring.
FUEL INJECTORSÐ3.0L
WARNING: THE 3.0L MPI FUEL SYSTEM IS UNDER
A CONSTANT PRESSURE OF APPROXIMATELY 330
KPA (48 PSI). PERFORM FUEL PRESSURE
RELEASE PROCEDURE BEFORE SERVICING THE
FUEL INJECTORS.
REMOVAL
(1) Perform the Fuel Pressure Release Procedure.
(2) Disconnect negative cable from battery.
(3) The fuel rail must be removed first to service
the injectors. Refer to Fuel Injector Rail Assembly
Removal in this section.
(4) Label each injector connector with its cylinder
number. Disconnect electrical connector from injector.
(5) Position fuel rail assembly so that the fuel
injectors are easily accessible.
(6) Remove injector clip from fuel rail and injector
(Fig. 54).
(7) Pull injector straight out of fuel rail receiver
cup (Fig. 55).
(8) Check injector O-ring for damage. If O-ring is
damaged, it must be replaced. If injector is to be
reused, a protective cap must be installed on the
injector tip to prevent damage.
(9) Repeat procedure for remaining injectors.
INSTALLATION
(1) Before installing an injector, the rubber O-ring
must be lubricated with a drop of clean engine oil to
aid in installation.
(2) Being careful not to damage O-ring, install
injector nozzle end into fuel rail receiver cap.
(3) Install injector clip by sliding open end into
top slotof the injector. The edge of the receiver cup
will slide into the side slots of clip (Fig. 55)
(4) Repeat steps for remaining injectors.
(5) Install fuel rail assembly. Refer to Fuel Rail
Assembly Installation in this section.
(6) Connect electrical connectors to injectors in cor-
rect order.
(7) Connect negative battery cable.
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.
(8) With the ignition key in ON position, access
the DRB scan tool ASD Fuel System Test to pressur-
ize the fuel system. Check for leaks.
Fig. 54 Fuel Injector and RailÐTypical
Fig. 55 Servicing Fuel InjectorÐTypical
NSFUEL SYSTEM 14 - 25
REMOVAL AND INSTALLATION (Continued)

THROTTLE BODY....................... 64
THROTTLE POSITION SENSOR............ 65
UPSTREAM OXYGEN SENSOR............. 68
SPECIFICATIONS
TORQUE.............................. 72SPECIAL TOOLS
FUEL................................. 72
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 PCMprogramming. Input from the oxygen (O2S) sensor is
not monitored during OPEN LOOP modes.
During CLOSED LOOP modes the PCM does mon-
itor the O2S sensor input. This input indicates to the
PCM whether or not the calculated injector pulse
width results in the ideal air/fuel ratio of 14.7 parts
air to 1 part fuel. By monitoring the exhaust oxygen
content through the O2S sensor, the PCM can fine
tune the injector pulse width. Fine tuning injector
pulse width allows the PCM to achieve optimum fuel
economy combined with low emissions.
The multi-port fuel injection system has the follow-
ing modes of operation:
²Ignition switch ON (zero RPM)
²Engine start-up
²Engine warm-up
²Cruise (Idle)
²Acceleration
²Deceleration
²Wide Open Throttle
²Ignition switch OFF
The engine start-up (crank), engine warm-up, and
wide open throttle modes are OPEN LOOP modes.
Under most operating conditions, the acceleration,
deceleration, and cruise modes,with the engine at
operating temperatureare CLOSED LOOP modes.
IGNITION SWITCH ON (ZERO RPM) MODE
When the multi-port fuel injection system is acti-
vated by the ignition switch, the following actions
occur:
²The PCM determines atmospheric air pressure
from the MAP sensor input to determine basic fuel
strategy.
²The PCM monitors the coolant temperature sen-
sor and throttle position sensor input. The PCM mod-
ifies fuel strategy based on this input.
When the key is in the ON position and the engine
is not running (zero rpm), the Automatic Shutdown
(ASD) relay and fuel pump relay are not energized.
Therefore 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
actions occur when the starter motor is engaged.
If the PCM receives the camshaft position sensor
and crankshaft position sensor signals, it energizes
the ASD relay and fuel pump relay. These relays sup-
ply battery voltage to the fuel pump, fuel injectors,
14 - 30 FUEL SYSTEMNS
SPECIFICATIONS (Continued)

Shutdown (ASD) RelayÐPCM Output in this section
for relay operation.
TORQUE CONVERTER CLUTCH SOLENOIDÐPCM
OUTPUT
Three-speed automatic transaxles use a torque con-
verter clutch solenoid. The PCM controls the engage-
ment of the torque converter clutch through the
solenoid. The torque converter clutch is engaged only
in direct drive mode. Refer to Group 21 for transaxle
information.
MALFUNCTION INDICATOR (CHECK ENGINE)
LAMPÐPCM OUTPUT
The PCM supplies the malfunction indicator (check
engine) lamp on/off signal to the instrument panel
through the CCD Bus. The CCD Bus is a communi-
cations port. Various modules use the CCD Bus to
exchange information.
The Check Engine lamp comes on each time the
ignition key is turned ON and stays on for 3 seconds
as a bulb test.
The Malfunction Indicator Lamp (MIL) stays on
continuously, when the PCM has entered a Limp-In
mode or identified a failed emission component. Dur-
ing Limp-in Mode, the PCM attempts to keep the
system operational. The MIL signals the need for
immediate service. In limp-in mode, the PCM com-
pensates for the failure of certain components that
send incorrect signals. The PCM substitutes for the
incorrect signals with inputs from other sensors.
If the PCM detects active engine misfire severe
enough to cause catalyst damage, it flashes the MIL.
At the same time the PCM also sets a Diagnostic
Trouble Code (DTC).
For signals that can trigger the MIL (Check
Engine Lamp) refer to Group 25, On-Board
Dianostics.
SOLID STATE FAN RELAYÐPCM OUTPUT
The radiator fan runs at a variable speed depend-
ing on coolant temperature and A/C system pressure.
The radiator fan circuit contains a Solid State Fan
Relay (SSFR). Refer to the Group 8W for a circuit
schematic.
A 5 volt signal is supplied to the SSFR. The PCM
provides a pulsed ground for the SSFR. Depending
upon the amount of pulse on time, the SSFR puts out
a proportional voltage to the fan motor at the lower
speed. For instance, if the on time is 30 percent, then
the voltage to the fan motor will be 3.6 volts.
When engine coolant reaches approximately 102ÉC
(215ÉF) the PCM grounds the SSFR relay. If engine
coolant reaches 207ÉC (225ÉF) the PCM grounds the
high speed ground relay and high speed fan relay. If
the fan operates at high speed, the PCM de-energizes
the high speed relay and high speed ground relay
when coolant temperature drops to approximately
101ÉC (214ÉF). When coolant temperature drops to
101ÉC (214ÉF) the fan operates at low speed. The
PCM de-energizes the low speed relay when coolant
temperature drops to approximately 93ÉC (199ÉF).
Also, when the air conditioning pressure switch
closes, the fan operates at high speed. The air condi-
tioning switch closes at 285 psi610 psi. When air
conditioning pressure drops approximately 40 psi, the
pressure switch opens and the fan operates at low
speed.
The SSFR relay is located on the left front inner
frame just behind the radiator (Fig. 42).
SPEED CONTROL SOLENOIDSÐPCM OUTPUT
The speed control vacuum and vent solenoids are
operated by the PCM. When the PCM supplies a
ground to the vacuum and vent solenoids, the speed
control system opens the throttle plate. When the
PCM removes the ground from the vacuum and vent
solenoids, the throttle blade closes. The PCM bal-
Fig. 41 Ignition Coil Ð3.3/3.8L
Fig. 42 Fan Control Module
14 - 46 FUEL SYSTEMNS
DESCRIPTION AND OPERATION (Continued)

²The PCM grounds the coil side of the relay
through terminal number 85.
²Terminal number 86 supplies voltage to the coil
side of the relay.
²When the PCM de-energizes the ASD and fuel
pump relays, terminal number 87A connects to termi-
nal 30. This is the Off position. In the off position,
voltage is not supplied to the rest of the circuit. Ter-
minal 87A is the center terminal on the relay.
²When the PCM energizes the ASD and fuel
pump relays, terminal 87 connects to terminal 30.
This is the On position. Terminal 87 supplies voltage
to the rest of the circuit.
TESTING
The following procedure applies to the ASD and
fuel pump relays.
(1) Remove relay from connector before testing.
(2) With the relay removed from the vehicle, use
an ohmmeter to check the resistance between termi-
nals 85 and 86. The resistance should be between 75
65 ohms.
(3) Connect the ohmmeter between terminals 30
and 87A. The ohmmeter should show continuity
between terminals 30 and 87A.
(4) Connect the ohmmeter between terminals 87
and 30. The ohmmeter should not show continuity at
this time.
(5) Connect one end of a jumper wire (16 gauge or
smaller) to relay terminal 85. Connect the other end
of the jumper wire to the ground side of a 12 volt
power source.
(6) Connect one end of another jumper wire (16
gauge or smaller) to the power side of the 12 volt
power source.Do not attach the other end of the
jumper wire to the relay at this time.
WARNING: DO NOT ALLOW OHMMETER TO CON-
TACT TERMINALS 85 OR 86 DURING THIS TEST.(7) Attach the other end of the jumper wire to
relay terminal 86. This activates the relay. The ohm-
meter should now show continuity between relay ter-
minals 87 and 30. The ohmmeter should not show
continuity between relay terminals 87A and 30.
(8) Disconnect jumper wires.
(9) Replace the relay if it did not pass the continu-
ity and resistance tests. If the relay passed the tests,
it operates properly. Check the remainder of the ASD
and fuel pump relay circuits. Refer to group 8W, Wir-
ing Diagrams.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
To perform a complete test of the MAP sensor and
its circuitry, refer to the DRB scan tool and appropri-
ate Powertrain Diagnostics Procedures manual. To
test the MAP sensor only, refer to the following:
CAUTION: When testing the MAP sensor, be sure
that the harness wires are not damaged by the test
meter probes.
(1) Test the MAP sensor output voltage at the
MAP sensor connector between terminals 2 and 3
(Fig. 95). With the ignition switch ON and the engine
not running, output voltage should be 4 to 5 volts.
The voltage should drop to 1.5 to 2.1 volts with a hot,
neutral idle speed condition. If OK, go to next step. If
not OK, go to step 3.
(2) Test PCM terminal 36 for the same voltage
described in the previous step to verify wire harness
condition. Repair as required.
(3) Test the MAP sensor ground circuit at sensor
connector terminal 1 and PCM terminal 43. If OK, go
to next step. If not OK, repair as required.
(4) Test MAP sensor supply voltage between sen-
sor connector terminals 2 and 1 with the key ON.
The voltage should be approximately 5 volts (6.5V).
Five volts (6.5V) should also be at terminal 61 of the
Fig. 94 ASD and Fuel Pump Relay Terminals
Fig. 95 MAP Sensor Connector
14 - 60 FUEL SYSTEMNS
DIAGNOSIS AND TESTING (Continued)

PCM. If OK, replace MAP sensor. If not OK, repair or
replace the wire harness as required.
HEATED OXYGEN SENSOR
Use an ohmmeter to test the heating element of
the oxygen sensors. Disconnect the electrical connec-
tor from each oxygen sensor. The white wires in the
sensor connector are the power and ground circuits
for the heater. Connect the ohmmeter test leads to
terminals of the white wires in the heated oxygen
sensor connector. Replace the heated oxygen sensor if
the resistance is not between 4 and 7 ohms.
KNOCK SENSOR
The engine knock sensor is affected by a number of
factors. A few of these are: ignition timing, cylinder
pressure, fuel octane, etc. The knock sensor gener-
ates an AC voltage whose amplitude increases with
the increase of engine knock. The knock sensor can
be tested with a digital voltmeter. The RMS voltage
starts at about 20mVac (at about 700 rpm) and
increases to approximately 600 mVac (5000 rpm). If
the output falls outside of this range a DTC will be
set.
CAMSHAFT AND CRANKSHAFT POSITION SENSOR
Refer to Group 8D, Ignition for Diagnosis and Test-
ing of Camshaft and Crankshaft Sensors.
ENGINE COOLANT TEMPERATURE SENSOR
(1) With the key off, disconnect wire harness con-
nector from coolant temperature sensor (Fig. 96) or
(Fig. 97) or (Fig. 98).
(2) Connect a high input impedance (digital) volt-
ohmmeter to terminals A and B (Fig. 99). The ohm-
meter should read as follows:
(a) ECT STET at normal operating temperature
around 200ÉF should read approximately 700 to
1,000 ohms.
(b) ECT STET at room temperature around 70ÉF
ohmmeter should read approximately 7,000 to
13,000 ohms.
(3) Test the resistance of the wire harness between
the PCM connector terminal 26 and the sensor har-
ness connector. Also check for continuity between
PCM connector terminal 43 and the sensor harness
connector. Refer to Group 8W, Wiring diagrams for
Fig. 96 Engine Coolant Temperature SensorÐ2.4L
Fig. 97 Engine Coolant Temperature SensorÐ3.0L
Fig. 98 Engine Coolant Temperature SensorÐ3.3/
3.8L
NSFUEL SYSTEM 14 - 61
DIAGNOSIS AND TESTING (Continued)

FUEL DELIVERY SYSTEMÐ2.5L DIESEL ENGINE
INDEX
page page
DESCRIPTION AND OPERATION
FUEL DRAIN TUBES..................... 7
FUEL FILTER/WATER SEPARATOR.......... 4
FUEL GAUGE SENDING UNIT.............. 4
FUEL HEATER RELAY.................... 8
FUEL HEATER.......................... 8
FUEL INJECTION PUMP.................. 5
FUEL INJECTORS....................... 6
FUEL SHUTDOWN SOLENOID............. 5
FUEL SYSTEM PRESSURE WARNING....... 3
FUEL TANK MODULE.................... 4
FUEL TANK............................ 3
FUEL TUBES/LINES/HOSES AND CLAMPSÐ
LOW-PRESSURE TYPE................. 6
HIGH-PRESSURE FUEL LINES............. 7
INTRODUCTION........................ 3
QUICK-CONNECT FITTINGSÐLOW PRESSURE
TYPE............................... 7
WASTEGATE (TURBOCHARGER)........... 8
DIAGNOSIS AND TESTING
AIR IN FUEL SYSTEM................... 11
FUEL HEATER RELAY TEST.............. 12
FUEL INJECTION PUMP TEST............. 12
FUEL INJECTOR SENSOR TEST........... 12
FUEL INJECTOR TEST.................. 12
FUEL SHUTDOWN SOLENOID TEST........ 13
FUEL SUPPLY RESTRICTIONS............ 13GENERAL INFORMATION................. 9
HIGH-PRESSURE FUEL LINE LEAK TEST.... 14
VISUAL INSPECTION..................... 9
WASTEGATE (TURBOCHARGER).......... 14
SERVICE PROCEDURES
AIR BLEED PROCEDURES............... 14
FUEL INJECTION PUMP TIMING........... 15
REMOVAL AND INSTALLATION
ACCELERATOR PEDAL.................. 16
AIR CLEANER ELEMENT................. 16
FUEL DRAIN TUBES.................... 16
FUEL FILTER/WATER SEPARATOR......... 16
FUEL HEATER RELAY................... 17
FUEL HEATER......................... 17
FUEL INJECTION PUMP................. 19
FUEL INJECTORS...................... 22
FUEL LEVEL SENSOR................... 18
FUEL RESERVOIR MODULE.............. 25
FUEL SHUTDOWN SOLENOID............ 23
FUEL TANK........................... 23
HIGH-PRESSURE LINES................. 26
SPECIFICATIONS
FUEL INJECTOR FIRING SEQUENCE....... 27
FUEL SYSTEM PRESSURE............... 27
FUEL TANK CAPACITY.................. 27
IDLE SPEED.......................... 27
DESCRIPTION AND OPERATION
INTRODUCTION
This Fuel Delivery section will cover components
not controlled by the PCM. For components con-
trolled by the PCM, refer to the Fuel Injection Sys-
temÐ2.5L Diesel Engine section of this group.
The fuel heater relay, fuel heater and fuel gauge
are not operated by the PCM. These components are
controlled by the ignition (key) switch. All other fuel
system electrical components necessary to operate
the engine are controlled or regulated by the PCM.
FUEL SYSTEM PRESSURE WARNING
WARNING: HIGH±PRESSURE FUEL LINES DELIVER
DIESEL FUEL UNDER EXTREME PRESSURE FROM
THE INJECTION PUMP TO THE FUEL INJECTORS.
THIS MAY BE AS HIGH AS 45,000 KPA (6526 PSI).
USE EXTREME CAUTION WHEN INSPECTING FORHIGH±PRESSURE FUEL LEAKS. INSPECT FOR
HIGH±PRESSURE FUEL LEAKS WITH A SHEET OF
CARDBOARD (Fig. 1). HIGH FUEL INJECTION
PRESSURE CAN CAUSE PERSONAL INJURY IF
CONTACT IS MADE WITH THE SKIN.
FUEL TANK
The fuel tank and tank mounting used with the
diesel powered engine is the same as used with gas-
oline powered models, although the fuel tank module
is different.
The fuel tank contains the fuel tank module and
two rollover valves. Two fuel lines are routed to the
fuel tank module. One line is used for fuel supply to
the fuel filter/water separator. The other is used to
return excess fuel back to the fuel tank.
The fuel tank module contains the fuel gauge elec-
trical sending unit.An electrical fuel pump is not
used with the diesel engine.
NS/GSFUEL SYSTEMÐ2.5L DIESEL ENGINE/2.0L GAS ENGINE 14 - 3

For periodic draining of water from the bowl, refer
to Fuel Filter/Water Separator Removal/Installation
in this group.
FUEL SHUTDOWN SOLENOID
The fuel shutdown solenoid is controlled and
operated by the PCM.
The fuel shutdown (shut-off) solenoid is used to
electrically shut off the diesel fuel supply to the high-
pressure fuel injection pump. The solenoid is
mounted to the rear of the injection pump (Fig. 4).
The solenoid controls starting and stopping of the
engine regardless of the position of the accelerator
pedal. When the ignition (key) switch is OFF, the
solenoid is shut off and fuel flow is not allowed to the
fuel injection pump. When the key is placed in the
ON or START positions, fuel supply is allowed at the
injection pump.
FUEL INJECTION PUMP
The fuel injection pump is a mechanical distribu-
tor±type, Bosch VP36 series (Fig. 5). A gear on the
end of the injection pump shaft meshes with the
drive gear at the front of engine. The pump is
mechanically timed, relative to the position of the
cam and crankshaft. The PCM can make adjust-
ments to the timing of the injection pump.
The injection pump contains the fuel shutdown
solenoid, fuel temperature sensor, control sleeve sen-
sor, fuel quantity actuator and the fuel timing sole-
noid (Fig. 5).In the electronically controlled injection pump, the
pump plunger works the same as the pump plunger
in a mechanically controlled injection pump, but the
amount of fuel and the time the fuel is injected is
controlled by the vehicle's PCM, instead of by a
mechanical governor assembly. A solenoid controlled
by the PCM is used in place of the mechanical gov-
ernor assembly, and it moves a control sleeve inside
the pump that regulates the amount of fuel being
injected. There is no mechanical connection between
the accelerator pedal and the electronically controlled
injection pump. Instead, a sensor connected to the
accelerator pedal sends a signal to the PCM that rep-
resents the actual position of the accelerator pedal.
The PCM uses this input, along with input from
other sensors to move the control sleeve to deliver
the appropriate amount of fuel. This system is known
as ªDrive-By-Wireº
The actual time that the fuel is delivered is very
important to the diesel combustion process. The PCM
monitors outputs from the engine speed sensor (fly-
wheel position in degrees), and the fuel injector sen-
sor (mechanical movement within the #1 cylinder
fuel injector). Outputs from the Accelerator Pedal
Position sensor, engine speed sensor (engine rpm)
and engine coolant temperature sensor are also used.
The PCM will then compare its set values to these
outputs to electrically adjust the amount of fuel tim-
ing (amount of advance) within the injection pump.
This is referred to as ªClosed Loopº operation. The
PCM monitors fuel timing by comparing its set value
to when the injector #1 opens. If the value is greater
than a preset value a fault will be set.
Fig. 4 Fuel Shutdown Solenoid and Overflow Valve
Location
Fig. 5 Fuel Injection Pump
NS/GSFUEL SYSTEMÐ2.5L DIESEL ENGINE/2.0L GAS ENGINE 14 - 5
DESCRIPTION AND OPERATION (Continued)

FUEL HEATER
The fuel heater is used to prevent diesel fuel from
waxing during cold weather operation. The fuel
heater is located in the bottom plastic bowl of the
fuel filter/water separator (Fig. 10).
The element inside the heater assembly is made of
a Positive Temperature Coefficient (PTC) material,
and has power applied to it by the fuel heater relayanytime the ignition key is in the ªonº position. PTC
material has a high resistance to current flow when
its temperature is high, which means that it will not
generate heat when the temperature is above a cer-
tain value. When the temperature is below 7ÉC (45É
F), the resistance of the PTC element is lowered, and
allows current to flow through the fuel heater ele-
ment warming the fuel. When the temperature is
above 29ÉC (85É F), the PTC element's resistance
rises, and current flow through the heater element
stops.
Voltage to operate the fuel heater is supplied from
the ignition (key) switch and through the fuel heater
relay. Refer to the following Fuel Heater Relay for
additional information.The fuel heater and fuel
heater relay are not controlled by the Power-
train Control Module (PCM).
Current draw for the heater element is 150 watts
at 14 volts (DC).
FUEL HEATER RELAY
Voltage to operate the fuel heater is supplied from
the ignition (key) switch through the fuel heater
relay.The PCM is not used to control this relay.
The fuel heater relay is located in the PDC. The
PDC is located next to the battery in the engine com-
partment (Fig. 11). For the location of the relay
within the PDC, refer to label on PDC cover.
WASTEGATE (TURBOCHARGER)
Refer to Group 11, Exhaust System and Intake
Manifold for information.
Fig. 9 Fuel Drain Tubes
Fig. 10 Fuel Heater Temperature Sensor and
Element LocationFig. 11 Relay Location
14 - 8 FUEL SYSTEMÐ2.5L DIESEL ENGINE/2.0L GAS ENGINENS/GS
DESCRIPTION AND OPERATION (Continued)

A defective fuel injection pump, defective fuel tim-
ing solenoid or misadjusted mechanical pump timing
can cause starting problems or prevent the engine
from revving up. It can also cause:
²Engine surge at idle
²Rough idle (warm engine)
²Low power
²Excessive fuel consumption
²Poor performance
²Low power
²Black smoke from the exhaust
²Blue or white fog like exhaust
²Incorrect idle or maximum speed
The electronically controlled fuel pump has no
mechanical governor like older mechanically con-
trolled fuel pumps. Do not remove the top cover of
the fuel pump, or the screws fastening the wiring
pigtail to the side of the pump.The warranty of
the injection pump and the engine may be void
if those seals have been removed or tampered
with.
FUEL SUPPLY RESTRICTIONS
LOW±PRESSURE LINES
Restricted or Plugged supply lines or fuel filter can
cause a timing fault that will cause the PCM to oper-
ate the engine in a ªLimp Homeº mode. See the
introduction of the Fuel Injection System in this
group for more information on the Limp Home mode.
Fuel supply line restrictions can cause starting prob-
lems and prevent the engine from revving up. The
starting problems include; low power and blue or
white fog like exhaust. Test all fuel supply lines for
restrictions or blockage. Flush or replace as neces-
sary. Bleed the fuel system of air once a fuel supply
line has been replaced. Refer to the Air Bleed Proce-
dure section of this group for procedures.
HIGH±PRESSURE LINES
Restricted (kinked or bent) high±pressure lines can
cause starting problems, poor engine performance
and black smoke from exhaust.
Examine all high±pressure lines for any damage.
Each radius on each high±pressure line must be
smooth and free of any bends or kinks.
Replace damaged, restricted or leaking high±pres-
sure fuel lines with the correct replacement line.
CAUTION: The high±pressure fuel lines must be
clamped securely in place in the holders. The lines
cannot contact each other or other components. Do
not attempt to weld high±pressure fuel lines or to
repair lines that are damaged. Only use the recom-
mended lines when replacement of high±pressure
fuel line is necessary.
FUEL SHUTDOWN SOLENOID TEST
Since diesel fuel injection does not use spark plugs
to start combustion, the only way to stop the engine
is to cut off the fuel supply. This is done with the
Fuel Shutdown Solenoid. If the engine cranks, but
refuses to start, it may be caused by a defective fuel
shutdown solenoid.
The fuel shutdown solenoid is not controlled
or operated by the PCM.Voltage to operate the
solenoid is supplied from the ignition (key) switch.
NOTE: Although the fuel shutdown solenoid is not
operated by the PCM, if the Fuel Shutdown Solenoid
has been disconnected, and the key turned on, the
PCM will sense that the solenoid is not in the circuit,
and will switch to a ªLimp Homeº mode. After recon-
necting the solenoid, the PCM will have to be reset
by clearing the codes with the DRBIII scan tool, or
disconnecting the vehicle's battery for several min-
utes. The DRBIII scan tool is the preferred method
for resetting the PCM. Refer to the 1998 GS 2.5L Die-
sel Powertrain Diagnostic Manual for procedure.
The fuel shutdown (shut±off) solenoid is used to
electrically shut off the diesel fuel supply to the high-
±pressure fuel injection pump. The solenoid is
mounted to the rear of the injection pump (Fig. 23).
The solenoid controls starting and stopping of the
engine regardless of the position of the accelerator
pedal. When the ignition (key) switch is OFF, the sole-
noid is shut off and fuel flow is not allowed to the fuel
injection pump. When the key is placed in the ON or
Fig. 23 Fuel Shutdown Solenoid Location
NS/GSFUEL SYSTEMÐ2.5L DIESEL ENGINE/2.0L GAS ENGINE 14 - 13
DIAGNOSIS AND TESTING (Continued)