the intake manifold. Refer to Group 11, Exhaust Sys-
tem and Intake Manifold for information.
(21) Be sure that the vacuum hoses to the vacuum
pump are connected and not leaking. The pump is
located on the front of engine (internal) and is driven
from the crankshaft gear and chain (Fig. 20). Discon-
nect the hose and check for minimum vacuum from
the pump. Refer to Group 5, Brake System for spec-
ifications and procedures.(22) Be sure that the accessory drive belt is not
damaged or slipping.
(23) Verify there is a good connection at the engine
speed sensor. Refer to the Fuel Injection System in
this section for location of the engine speed sensor
location.
(24) Verify there is a good connection at the Mass
Air Flow Sensor, which is a part of the air intake
assembly.
AIR IN FUEL SYSTEM
Air will enter the fuel system whenever the fuel
supply lines, fuel filter/water separator, fuel filter
bowl, injection pump, high±pressure lines or injectors
are removed or disconnected. Air will also enter the
fuel system whenever the fuel tank has been run
empty.
Air trapped in the fuel system can result in hard
starting, a rough running engine, engine misfire, low
power, excessive smoke and fuel knock. After service
is performed, air must be bled from the system
before starting the engine.
Inspect the fuel system from the fuel tank to the
injectors for loose connections. Leaking fuel is an
indicator of loose connections or defective seals. Air
can also enter the fuel system between the fuel tank
and the injection pump. Inspect the fuel tank and
fuel lines for damage that might allow air into the
system.
For air bleeding, refer to Air Bleed Procedure in
the Service Procedures section of this group.
Fig. 18 Vehicle Speed SensorÐTypical
Fig. 19 Engine Coolant Temperature Sensor
Location
Fig. 20 Vacuum Pump at Front of Engine
NS/GSFUEL SYSTEMÐ2.5L DIESEL ENGINE/2.0L GAS ENGINE 14 - 11
DIAGNOSIS AND TESTING (Continued)
FUEL HEATER RELAY TEST
The fuel heater relay is located in the Power Dis-
tribution Center (PDC). Refer to RelaysÐOperation/
Testing in Fuel Ingection System section of this
group for test procedures.
FUEL INJECTOR TEST
The fuel injection nozzels, located on the engine
cylinder head, spray fuel under high pressure into
the individual combustion chambers. Pressurized
fuel, delivered by the fuel injection pump, unseats a
spring-loaded needle valve inside the injector, and
the fuel is atomized as it escapes through the injector
opening into the engine's combustion chamber. If the
fuel injector does not operate properly, the engine
may misfire, or cause other driveability problems.
A leak in the injection pump±to±injector high±pres-
sure fuel line can cause many of the same symptoms
as a malfunctioning injector. Inspect for a leak in the
high±pressure lines before checking for a malfunc-
tioning fuel injector.
WARNING: THE INJECTION PUMP SUPPLIES HIGH-
±PRESSURE FUEL OF UP TO APPROXIMATELY
45,000 KPA (6526 PSI) TO EACH INDIVIDUAL INJEC-
TOR THROUGH THE HIGH±PRESSURE LINES. FUEL
UNDER THIS AMOUNT OF PRESSURE CAN PENE-
TRATE THE SKIN AND CAUSE PERSONAL INJURY.
WEAR SAFETY GOGGLES AND ADEQUATE PRO-
TECTIVE CLOTHING. AVOID CONTACT WITH FUEL
SPRAY WHEN BLEEDING HIGH±PRESSURE FUEL
LINES.
WARNING: DO NOT BLEED AIR FROM THE FUEL
SYSTEM OF A HOT ENGINE. DO NOT ALLOW FUEL
TO SPRAY ONTO THE EXHAUST MANIFOLD WHEN
BLEEDING AIR FROM THE FUEL SYSTEM.
To determine which fuel injector is malfunctioning,
run the engine and loosen the high±pressure fuel line
nut at the injector (Fig. 21). Listen for a change in
engine speed. If engine speed drops, the injector was
operating normally. If engine speed remains the
same, the injector may be malfunctioning. After test-
ing, tighten the line nut to 30 N´m (22 ft. lbs.)
torque. Test all injectors in the same manner one at
a time.
Once an injector has been found to be malfunction-
ing, remove it from the engine and test it. Refer to
the Removal/Installation section of this group for pro-
cedures.
After the injector has been removed, install it to a
bench±mount injector tester. Refer to operating
instructions supplied with tester for procedures.
The opening pressure or ªpopº pressure should be
15,000±15,800 kPa (2175±2291 psi). If the fuel injec-tor needle valve is opening (ªpoppingº) to early or to
late, replace the injector.
FUEL INJECTOR SENSOR TEST
The fuel injector sensor is used only on the fuel
injector for the number±1 cylinder (Fig. 22). It is not
used on the injectors for cylinders number 2, 3, or 4.
To test the sensor, unplug the sensor connector
(Fig. 22) from the engine wiring harness. Check
resistance across terminals. Resistance should be 110
ohms610 ohms at 20ÉC (68ÉF). Replace sensor if
specification cannot be met.
FUEL INJECTION PUMP TEST
The injection pump is not to be serviced or
the warranty may be voided. If the injection
pump requires service, the complete assembly
must be replaced.
Incorrect injection pump timing (mechanical or
electrical) can cause poor performance, excessive
smoke and emissions and poor fuel economy.
Fig. 21 Typical Inspection of Fuel Injector
Fig. 22 Fuel Injector Sensor Location
14 - 12 FUEL SYSTEMÐ2.5L DIESEL ENGINE/2.0L GAS ENGINENS/GS
DIAGNOSIS AND TESTING (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)
START positions, fuel supply is allowed at the injec-
tion pump.
(1) Disconnect the electrical pigtail connector (test
connector) (Fig. 23) from the main engine wiring har-
ness. Do not disconnect wiring directly at solenoid.
(2) Connect the leads of a voltmeter between a
good ground and the disconnected engine wiring har-
ness.
(3) Turn the key to the ON position. Do not
attempt to start engine.
(4) 12V+ should be observed at wiring harness. If
not, refer to Group 8, Wiring for wiring schematics
and repair as necessary.
(5) T
urn the key to the START position. 12V+ should
be observed at wiring harness. If not, refer to Group 8,
Wiring for wiring schematics and repair as necessary.
The fault may be in the ignition (key) switch.
12V+ must be observed in both the ON and START
positions. If 12V+ was observed, proceed to the next
step.
(6) With key still in the ON position, connect and
disconnect the wiring harness to the solenoid. As this
is done, a clicking noise should be heard coming from
the solenoid. If not, replace solenoid. Refer to Fuel
Shutdown Solenoid in the Removal/Installation sec-
tion of this group for procedures.
HIGH-PRESSURE FUEL LINE LEAK TEST
High±pressure fuel line leaks can cause starting
problems and poor engine performance.
WARNING: DUE TO EXTREME FUEL PRESSURES
OF UP TO 45,000 KPA (6526 PSI), USE EXTREME
CAUTION WHEN INSPECTING FOR HIGH±PRESSURE
FUEL LEAKS. DO NOT GET YOUR HAND, OR ANY
PART OF YOUR BODY NEAR A SUSPECTED LEAK.
INSPECT FOR HIGH±PRESSURE FUEL LEAKS WITH
A SHEET OF CARDBOARD. HIGH FUEL INJECTION
PRESSURE CAN CAUSE PERSONAL INJURY IF
CONTACT IS MADE WITH THE SKIN.
Start the engine. Move the cardboard over the
high±pressure fuel lines and check for fuel spray onto
the cardboard (Fig. 24). If a high±pressure line con-
nection is leaking, bleed the system and tighten the
connection. Refer to the Air Bleed Procedure in this
group for procedures. Replace damaged, restricted or
leaking high±pressure 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.
WASTEGATE (TURBOCHARGER)
Refer to Group 11, Exhaust System and Intake
Manifold for information.
SERVICE PROCEDURES
AIR BLEED PROCEDURES
AIR BLEEDING AT FUEL FILTER
A certain amount of air may become trapped in the
fuel system when fuel system components are ser-
viced or replaced. Bleed the system as needed after
fuel system service according to the following proce-
dures.
WARNING: DO NOT BLEED AIR FROM THE FUEL
SYSTEM OF A HOT ENGINE. DO NOT ALLOW FUEL
TO SPRAY ONTO THE EXHAUST MANIFOLD WHEN
BLEEDING AIR FROM THE FUEL SYSTEM.
Some air enters the fuel system when the fuel fil-
ter or injection pump supply line is changed. This
small amount of air is vented automatically from the
injection pump through the fuel drain manifold tubes
if the filter was changed according to instructions.
Ensure the bowl of the fuel filter/water separator is
full of fuel
It may be necessary to manually bleed the system
if:
²The bowl of the fuel filter/water separator is not
partially filled before installation of a new filter
²The injection pump is replaced
Fig. 24 Typical Test for Leaks with Cardboard
14 - 14 FUEL SYSTEMÐ2.5L DIESEL ENGINE/2.0L GAS ENGINENS/GS
DIAGNOSIS AND TESTING (Continued)
²High±pressure fuel line connections are loosened
or lines replaced
²Initial engine start±up or start±up after an
extended period of no engine operation
²Running fuel tank empty
FUEL INJECTION PUMP BLEEDING
(1) If the fuel injection pump has been replaced,
air should be bled at the overflow valve before
attempting to start engine.
(a) Loosen the overflow valve (Fig. 25) at the
rear of the injection pump.
(b) Place a towel below the valve.
WARNING: WHEN CRANKING THE ENGINE TO
BLEED AIR FROM THE INJECTION PUMP, THE
ENGINE MAY START. PLACE THE TRANSMISSION
IN NEUTRAL OR PARK AND SET PARKING BRAKE
BEFORE ENGAGING THE STARTER MOTOR.
CAUTION: Do not engage the starter motor for
more than 30 seconds at a time. Allow 2 minutes
between cranking intervals.
(2) Crank the engine for 30 seconds at a time to
allow air trapped in the injection pump to vent out
the fuel injector drain tubes. Continue this procedure
until the engine starts. Observe the previous WARN-
ING and CAUTION.
(3) Tighten overflow valve.
HIGH±PRESSURE FUEL LINE BLEEDING
WARNING: THE INJECTION PUMP SUPPLIES HIGH-
±PRESSURE FUEL OF APPROXIMATELY 59,000 KPA
(8,557 PSI) TO EACH INDIVIDUAL INJECTOR
THROUGH THE HIGH±PRESSURE LINES. FUEL
UNDER THIS AMOUNT OF PRESSURE CAN PENE-
TRATE THE SKIN AND CAUSE PERSONAL INJURY.
WEAR SAFETY GOGGLES AND ADEQUATE PRO-
TECTIVE CLOTHING AND AVOID CONTACT WITH
FUEL SPRAY WHEN BLEEDING HIGH±PRESSURE
FUEL LINES.
WARNING: DO NOT BLEED AIR FROM THE FUEL
SYSTEM OF A HOT ENGINE. DO NOT ALLOW FUEL
TO SPRAY ONTO THE EXHAUST MANIFOLD WHEN
BLEEDING AIR FROM THE FUEL SYSTEM.
Bleed air from one injector at time.
(1) Loosen the high±pressure fuel line fitting at
the injector (Fig. 26).
(2) Crank the engine until all air has been bled
from the line.Do not operate the starter motor
for longer than 30 seconds. Wait 2 minutes
between cranking intervals.
(3) Start the engine and bleed one injector at a
time until the engine runs smoothly.
FUEL INJECTION PUMP TIMING
Refer to Removal/Installation and Adjusting Fuel
Pump Timing in this Group.
Fig. 25 Overflow Valve
Fig. 26 Bleeding High±Pressure Fuel LineÐTypical
NS/GSFUEL SYSTEMÐ2.5L DIESEL ENGINE/2.0L GAS ENGINE 14 - 15
SERVICE PROCEDURES (Continued)
REMOVAL AND INSTALLATION
ACCELERATOR PEDAL
CAUTION: Be careful not to damage or kink the
cable core wire (within the cable sheathing) while
servicing the accelerator pedal or throttle cable.
REMOVAL
(1) Disconnect electrical connector.
(2) Remove accelerator pedal mounting bracket
nuts. Remove accelerator pedal assembly.
INSTALLATION
(1) Place accelerator pedal assembly over studs
protruding from floor pan. Tighten mounting nuts to
5 N´m (46 in. lbs.) torque.
(2) Connect electrical connector.
(3) Before starting the engine, operate the acceler-
ator pedal to check for any binding.
AIR CLEANER ELEMENT
REMOVAL
(1) Remove hose clamp at Mass Air Flow Sensor.
(2) Remove hose from Mass Air Flow Sensor.(3) Loosen 2 clamps holding air cleaner housing
halves together.
(4) Remove left side of air cleaner housing.
(5) Remove element from air cleaner housing.
INSTALLATION
(1) Install a new element in housing.
(2) Position left side of housing.
(3) Snap clamps into place.
(4) Install hoses and clamps.
FUEL DRAIN TUBES
The fuel drain tubes (Fig. 28) are low±pressure
type.
Pull each tube from the injector for removal. Push
on for installation. Clamps are not required for these
tubes.
FUEL FILTER/WATER SEPARATOR
The fuel filter/water separator is located in the
engine compartment on the right side near the shock
tower. (Fig. 29).
The fuel filter/water separator assembly contains
the fuel filter, fuel heater element, and fuel drain
valve (Fig. 29).
DRAINING WATER FROM FILTER BOWL
Moisture (water) collects at the bottom of the filter/
separator in a plastic bowl. Water entering the fuel
injection pump can cause serious damage to the
pump.Note that the bulb will be illuminated for
approximately 2 seconds each time the key is
initially placed in the ON position. This is done
for a bulb check.
Fig. 27 Accelerator Pedal Mounting-Typical
Fig. 28 Fuel Drain Tubes
14 - 16 FUEL SYSTEMÐ2.5L DIESEL ENGINE/2.0L GAS ENGINENS/GS
(8) Disconnect the main engine wiring harness
from the glow plugs.
(9) Disconnect the four high±pressure fuel lines
from the fuel injection pump. Also disconnect fuel
lines at the fuel injectors. For procedures, refer to
High±Pressure Fuel Lines in this group. Place a rag
beneath the fittings to catch excess fuel.
(10) Remove plug from timing gear cover.
(11) The ªTop Dead Centerº (TDC) compression fir-
ing stroke must be determined as follows:
(a) Remove the valve cover, refer to Group 9,
Valve Cover Removal/Installation.
(b) Remove the right front tire and splash
shield. Using a socket attached to the end of crank-
shaft, rotate the engine (counterÐclockwise as
viewed from front).
(c) Rotate the engine until cylinder #4 rockers
are in between movement.
(d) Remove rocker arm assembly.
(e) Remove valve spring and keepers.CAU-
TION: When the piston is at TDC there is only
2 mm (.080 thousand) clearance between the
valve and piston.
(f) Let the valve set on top of piston. Install a
dial indicator to the top of the valve stem.
(g) Rotate engine back and forth to find the TDC
position with the indicator on the valve stem. Mark
the damper and timing cover for TDC.
NOTE: On later model 1997 engines, a hole in the
bottom of the clutch housing can be lined up with a
hole in the flywheel, allowing the engine to be held
at TDC with a special alignment tool, part # VM1035.(12) Remove injection pump drive gear nut (Fig.
41) and washer.CAUTION: Be very careful not to
drop the washer into the timing gear cover.
(13) A special 3±piece gear removal tool set
VM.1003 (Fig. 42) must be used to remove the injec-
tion pump drive gear from the pump shaft.
(a) Thread the adapter (Fig. 43) into the timing
cover.
(b) Thread the gear puller into the injection
pump drive gear (Fig. 43). This tool is also used to
hold the gear in synchronization during pump
removal.
(c) Remove the three injection pump±to±gear
cover mounting nuts (Fig. 44).CAUTION: This
step must be done to prevent breakage of the
Fig. 40 Engine Coolant Temperature Sensor
Fig. 41 Removing Pump Drive Gear Nut
Fig. 42 Pump Gear Tools
14 - 20 FUEL SYSTEMÐ2.5L DIESEL ENGINE/2.0L GAS ENGINENS/GS
REMOVAL AND INSTALLATION (Continued)
(14) Gauge reading should be at 0.60 mm. If not,
the pump must be rotated for adjustment:
(a) Loosen the three injection pump mounting
nuts at the mounting flanges. These flanges are
equipped with slotted holes. The slotted holes are
used to rotate and position the injection pump for
fuel timing. Loosen the three nuts just enough to
rotate the pump.
(b) Rotate the pumpclockwise(as viewed from
front) until .60 mm is indicated on the dial indica-
tor gauge.
(c) Tighten the three pump mounting nuts to 30
N´m (22 ft. lbs.) torque.
(d) Recheck the dial indicator after tightening
the pump mounting nuts. Gauge should still be
reading 0.60 mm. Loosen pump mounting nuts and
readjust if necessary.
(15) Remove dial indicator and adapter tools.
(16) Install access plug and washer to rear of
injection pump.
(17) Install plug at timing gear cover.
(18) Remove dial indicator from valve stem.
(19) Install valve spring and keepers.
(20) Install rocker arm assembly and tighten nuts.
(21) Install and connect the four high±pressure
fuel lines to the fuel injection pump. Also connect
fuel lines at the fuel injectors. For procedures, refer
to High±Pressure Fuel Lines in this group.
(22) Install electrical connector at engine coolant
temperature sensor.
(23) Connect electrical connector at fuel shutdown
solenoid.(24) Connect the main engine wiring harness to
the glow plugs.
(25) Connect the fuel timing solenoid pigtail har-
ness to the engine wiring harness.
(26) Connect the overflow valve/banjo fitting (fuel
return line assembly). Replace copper gaskets before
installing.
(27) Connect the rubber fuel return and supply
hoses to metal lines at pump. Tighten hose clamps to
2 N´m (20 in. lbs.) torque.
(28) Install generator assembly.
(29) Install engine accessory drive belt. Refer to
Group 7, Cooling System for procedures.
(30) Install negative battery cable to battery.
(31) Start the engine and bring to normal operat-
ing temperature.
(32) Check for fuel leaks.
FUEL INJECTORS
Four fuel injectors are used on each engine. Of these
four, two different types are used. The fuel injector used
on cylinder number one is equipped with a fuel injector
sensor (Fig. 47). The other three fuel injectors are iden-
tical.
Do not place the fuel injector equipped with
the fuel injector sensor into any other location
except the cylinder number one position.
REMOVAL
(1) Disconnect negative battery cable at battery.
(2) Thoroughly clean the area around the injector
with compressed air.
(3) Remove the fuel drain hoses (tubes) at each
injector (Fig. 48) being serviced. Each of these hoses
is slip±fit to the fitting on injector.
(4) Remove the high±pressure fuel line at injector
being removed. Refer to High±Pressure Fuel Lines in
this group for procedures.
(5) Remove the injector using special socket tool
number VM.1012A. When removing cylinder number
Fig. 46 Installing Dial Indicator and Special Adapter
Tools
Fig. 47 Fuel Injector SensorÐNumber±1 Cylinder
14 - 22 FUEL SYSTEMÐ2.5L DIESEL ENGINE/2.0L GAS ENGINENS/GS
REMOVAL AND INSTALLATION (Continued)