ABS ISUZU KB P190 2007 Workshop Repair Manual

6E–48 ENGINE DRIVEABILITY AND EMISSIONS
GENERAL DESCRIPTION FOR ECM AND
SENSORS
Engine Control Module (ECM)
The engine control module (ECM) is located on the
intake manifold. The ECM controls the following.
• Fuel metering system
• Ignition timing
• On-board diagnostics for electrical functions.
The ECM constantly observes the information from vari-
ous sensors. The ECM controls the systems that affect
vehicle performance. And it performs the diagnostic
function of the system.
The function can recognize operational problems, and
warn to the driver through the check engine lamp, and
store diagnostic trouble code (DTC). DTCs identify the
problem areas to aid the technician in marking repairs.
The input / output devices in the ECM include analog to
digital converts, signal buffers, counters and drivers.
The ECM controls most components with electronic
switches which complete a ground circuit when turned
on.
Inputs (Operating condition read):
• Battery voltage
• Electrical ignition
• Exhaust oxygen content
• Intake manifold pressure
• Intake air temperature
• Engine coolant temperature
• Crankshaft position • Knock signal
• Throttle position
• Vehicle speed
• Power steering pressure
• Air conditioning request on or off
Outputs (Systems controlled):
• Ignition control
• Fuel control
• Idle air control
• Fuel pump
• EVAP canister purge
• Air conditioning
• Diagnostics functions
Manifold Absolute Pressure (MAP) Sensor
The MAP sensor is a strain gage. A pressure strains the
resistance on the silicon base. At that time the
resistance value changes. And it changes voltage. In
other words it measures a pressure value. It is installed
to the intake manifold. Output voltage of the MAP
sensor is low as pressure is low.
(1) J1 Port
(2) J2 Port
12
C harac t eris t ic of MAP Sens or -R ef erenc e-
0
0.5 1
1.5 2
2.5
3
3.5 4
4.5 5
15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 Manifold Abs olute Press ure (KPa) (T ec h2 Reading)
Output Voltage (V)

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6E–52 ENGINE DRIVEABILITY AND EMISSIONS
GENERAL DESCRIPTION FOR FUEL
METERING
The fuel metering system starts with the fuel in the fuel
tank. An electric fuel pump, located in the fuel tank,
pumps fuel to the fuel rail through an in-line fuel filter.
The pump is designed to provide fuel at a pressure
above the pressure needed by the injectors.
A fuel pressure regulator in the fuel rail keeps fuel
available to the fuel injectors at a constant pressure.
A return line delivers unused fuel back to the fuel tank.
The basic function of the air/fuel metering system is to
control the air/fuel delivery to the engine. Fuel is
delivered to the engine by individual fuel injectors
mounted in the intake manifold.
The main control sensor is the heated oxygen sensor
located in the exhaust system. The heated oxygen
sensor reports to the ECM how much oxygen is in the
exhaust gas. The ECM changes the air/fuel ratio to the
engine by controlling the amount of time that fuel
injector is “On”.
The best mixture to minimize exhaust emissions is 14.7
parts of air to 1 part of gasoline by weight, which allows
the catalytic converter to operate most efficiently.
Because of the constant measuring and adjusting of the
air/fuel ratio, the fuel injection system is called a “closed
loop” system.
The ECM monitors signals from several sensors in
order to determine the fuel needs of the engine. Fuel is
delivered under one of several conditions called “mode”.
All modes are controlled by the ECM.
Battery Voltage Correction Mode
When battery voltage is low, the ECM will compensate
for the weak spark by increasing the following:
• The amount of fuel delivered.
• The idle RPM.
Clear Flood Mode
Clear a flooded engine by pushing the accelerator pedal
down all the way. The ECM then de-energizes the fuel
injectors. The ECM holds the fuel injectors de-energized
as long as the throttle remains above 75% and the
engine speed is below 800 RPM. If the throttle position
becomes less than 75%, the ECM again begins to pulse
the injectors ON and OFF, allowing fuel into the
cylinders.
Deceleration Fuel Cutoff (DFCO) Mode
The ECM reduces the amount of fuel injected when it
detects a decrease in the throttle position and the air
flow. When deceleration is very fast, the ECM may cut
off fuel completely. Until enable conditions meet the
engine revolution less 1000 rpm or manifold absolute
pressure less than 10 kPa.
Engine Speed/ Vehicle Speed/ Fuel Disable
Mode
The ECM monitors engine speed. It turns off the fuel
injectors when the engine speed increases above 6000
RPM. The fuel injectors are turned back on when
engine speed decreases below 3500 RPM.
Acceleration Mode
The ECM provides extra fuel when it detects a rapid
increase in the throttle position and the air flow.
Fuel Cutoff Mode
No fuel is delivered by the fuel injectors when the
ignition is OFF. This prevents engine run-on. In addition,
the ECM suspends fuel delivery if no reference pulses
are detected (engine not running) to prevent engine
flooding.
Starting Mode
When the ignition is first turned ON, the ECM energizes
the fuel pump relay for two seconds to allow the fuel
pump to build up pressure. The ECM then checks the
engine coolant temperature (ECT) sensor and the
throttle position sensor to determine the proper air/fuel
ratio for starting.
The ECM controls the amount of fuel delivered in the
starting mode by adjusting how long the fuel injectors
are energized by pulsing the injectors for very short
times.
Run Mode
The run mode has the following two conditions:
• Open loop
• Closed loop
When the engine is first started, the system is in “open
loop” operation. In “Open Loop,” the ECM ignores the
signal from the heated oxygen sensor (HO2S). It
calculates the air/fuel ratio based on inputs from the TP,
ECT, and MAP sensors.
The system remains in “Open Loop” until the following
conditions are met:
• The HO2S has a varying voltage output showing that it is hot enough to operate properly (this depends on
temperature).
• The ECT has reached a specified temperature.
• A specific amount of time has elapsed since starting the engine.
• Engine speed has been greater than a specified RPM since start-up.
The specific values for the above conditions vary with
different engines and are stored in the programmable
read only memory (PROM). When these conditions are
met, the system enters “closed loop” operation. In
“closed loop,” the ECM calculates the air/fuel ratio
(injector on-time) based on the signal from the HO2S.
This allows the air/fuel ratio to stay very close to 14.7:1.

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6E–72 ENGINE DRIVEABILITY AND EMISSIONS
TYPICAL SCAN DATA & DEFINITIONS (ENGINE DATA)
Use the Typical Values Table only after the On-Board Diagnostic System Check has been completed, no DTC(s) were
noted, and you have determined that the on-board diagnostics are functioning properly. Tech 2 values from a
properly-running engine may be used for comparison with the engine you are diagnosing.
Condition : Vehicle stopping, engine running, air conditioning off & after warm-up (Coolant temperature approximately
80 deg.)
Tech 2 ParameterUnitsIdle2000rpmDescription
1 Engine Speed rpm775 - 8751950 - 2050 The actual engine speed is measured by ECM from the
CKP sensor 58X signal.
2 Desired Idle Speed rpm825800 - 850 The desired engine idle speed that the ECMcommanding. The ECM compensates for various engine
loads.
3 Engine Coolant Temperature °C or °F80 - 9080 - 90 The ECT is measured by ECM from ECT sensor output
voltage. When the engine is normally warm upped, this
data displays approximately 80 °C or more.
4 Start Up ECT (Engine Coolant Temperature) °C or °FDepends on ECT
at start-upDepends on ECT at start-up Start-up ECT is measured by ECM from ECT sensor
output voltage when engine is started.
5Intake Air
Temperature °C or °FDepends on
ambient tempDepends on
ambient temp The IAT is measured by ECM from IAT sensor output
voltage. This data is changing by intake air temperature.
6 Start Up IAT (Intake Air Temperature) °C or °FDepends on IAT at
start-upDepends on IAT at start-up Start-up IAT is measured by ECM from IAT sensor output
voltage when engine is started.
7 Manifold Absolute Pressure kPa31 - 3625 - 30The MAP (kPa) is measured by ECM from MAP output
voltage. This data is changing by inlet manifold pressure.
8 Barometric Pressure kPaDepends on altitudeDepends on altitude The barometric pressure is measured by ECM from the
MAP sensor output voltage monitored during key up and
wide open throttle. This data is changing by altitude.
9 Throttle Position %02-4 Throttle position operating angle is measured by the ECM from throttle position output voltage. This should
display 0% at idle and 99 - 100% at full throttle.
10 Calculated Air Flow g/s3.5 -4.508.0 - 10.0 This displays calculated air mount from MAP sensor output. This data is changing by inlet manifold pressure.
11 Air Fuel Ratio14.6:114.6:1 This displays the ECM commanded value. In closed loop,this should normally be displayed around 14.2:1 - 14.7:1.
12 Spark Advance °CA8 - 1525 - 32 This displays the amount of spark advance being commanded by the ECM.
13 Engine Load %2 - 55 - 10 This displays is calculated by the ECM form engine
speed and MAF sensor reading. Engine load should
increase with an increase in engine speed or air flow
amount.
14 Injection Pulse Width ms1.0 - 3.0 3.0 - 4.0 This displays the amount of time the ECM is commanding each injector On during each engine cycle.
A longer injector pulse width will cause more fuel to be
delivered. Injector pulse width should increase with
increased engine load.
15 Fuel System Status Open Loop/ Close LoopClose LoopClose Loop When the engine is first started the system is in “OpenLoop” operation. In “Open Loop”, the ECM ignores the
signal from the oxygen sensors. When various conditions
(ECT, time from start, engine speed & oxygen sensor
output) are met, the system enters “Closed Loop”
operation. In “Closed Loop”, the ECM calculates the air
fuel ratio based on the signal from the oxygen sensors.
16 Knock Present Yes/NoNoNo This displays knock sensor detection status. When engine knock is occurred, displays "Yes".
17 Knock Counter--This displays the number of knock during a ignition cycle.
18 Knock Retard °CA00 This displays the commanded ignition spark timing retard
timing based on the signal from the knock sensor.
19 A/C Clutch Relay On/OffOffOff This displays whether the ECM has commanded the A/C compressor clutch “On” or “Off”.

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6E–74 ENGINE DRIVEABILITY AND EMISSIONS
TYPICAL SCAN DATA & DEFINITIONS (O2 SENSOR DATA)
Use the Typical Values Table only after the On-Board Diagnostic System Check has been completed, no DTC(s) were
noted, and you have determined that the on-board diagnostics are functioning properly. Tech 2 values from a
properly-running engine may be used for comparison with the engine you are diagnosing.
Condition : Vehicle stopping, engine running, air conditioning off & after warm-up (Coolant temperature approximately
80 deg.)
Tech 2 ParameterUnitsIdle2000rpmDescription
1 Engine Speed rpm710 - 8751950 - 2050 The actual engine speed is measured by ECM from the
CKP sensor 58X signal.
2 Desired Idle Speed rpm825800 - 850 The desired engine idle speed that the ECMcommanding. The ECM compensates for various engine
loads.
3 Engine Coolant Temperature °C or °F80 - 9080 - 90 The ECT is measured by ECM from ECT sensor output
voltage. When the engine is normally warm upped, this
data displays approximately 80 °C or more.
4 Start Up ECT (Engine Coolant Temperature) °C or °FDepends on ECT
at start-upDepends on ECT at start-up Start-up ECT is measured by ECM from ECT sensor
output voltage when engine is started.
5Intake Air
Temperature °C or °FDepends on
ambient tempDepends on
ambient temp The IAT is measured by ECM from IAT sensor output
voltage. This data is changing by intake air temperature.
6 Start Up IAT (Intake Air Temperature) °C or °FDepends on IAT at
start-upDepends on IAT at start-up Start-up IAT is measured by ECM from IAT sensor output
voltage when engine is started.
7 Manifold Absolute Pressure kPa31 - 3625 - 30The MAP (kPa) is measured by ECM from MAP output
voltage. This data is changing by inlet manifold pressure.
8 Barometric Pressure kPaDepends on altitudeDepends on altitude The barometric pressure is measured by ECM from the
MAP sensor output voltage monitored during key up and
wide open throttle. This data is changing by altitude.
9 Throttle Position %02 - 4 Throttle position operating angle is measured by the ECM from throttle position output voltage. This should
display 0% at idle and 99 - 100% at full throttle.
10 Calculated Air Flow g/s3.5 -4.508.0 - 10.0 This displays intake air amount. The mass air flow is measured by ECM from the MAF sensor output voltage.
11 Air Fuel Ratio14.6:114.6:1 This displays the ECM commanded value. In closedloop, this should normally be displayed around 14.2:1 -
14.7:1.
12 Fuel System Status Open Loop/ Close LoopClose LoopClose Loop When the engine is first started the system is in “OpenLoop” operation. In “Open Loop”, the ECM ignores the
signal from the oxygen sensors. When various
conditions (ECT, time from start, engine speed & oxygen
sensor output) are met, the system enters “Closed Loop”
operation. In “Closed Loop”, the ECM calculates the air
fuel ratio based on the signal from the oxygen sensors.
13 Engine Load %2 - 55 - 10 This displays is calculated by the ECM form engine
speed and MAF sensor reading. Engine load should
increase with an increase in engine speed or air flow
amount.
14B1 O2 Sensor Ready
(Bank 1)Ye s / N oYe sYes This displays the status of the exhaust oxygen sensor. This display will indicate “Yes” when the ECM detects a
fluctuating oxygen sensor output voltage sufficient to
allow closed loop operation. This will not occur unless
the oxygen sensor is warmed up.
15B1S1 Status
(Bank 1 Sensor 1)Rich / LeanRich / LeanRich / Lean This displays dependent on the exhaust oxygen sensor output voltage. Should fluctuate constantly “Rich” and
“Lean” in closed loop.
16 Fuel Trim Learned Yes/NoYe sYes When conditions are appropriate for enabling long term fuel trim corrections, fuel trim learn will display “Yes”.
This indicates that the long term fuel trim is responding
to the short term fuel trim. If the fuel trim lean displays
“No”, then long term fuel trim will not respond to changes
in short term fuel trim.

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6E–76 ENGINE DRIVEABILITY AND EMISSIONS
MISCELLANEOUS TEST
The state of each circuit can be tested by using
miscellaneous test menus. Especially when DTC
cannot be detected, a faulty circuit can be diagnosed by
testing each circuit by means of these menus.
Even DTC has been detected, the circuit tests using
these menus could help discriminate between a
mechanical trouble and an electrical trouble.
Connect Tech 2 and select “Powertrain”, “2.XL L4
HV240” & “Miscellaneous Test”.
F0: Lamps
F0: Malfunction Indicator Lamp
When the Tech 2 is operated, “Malfunction Indicator
Lamp (Check Engine Lamp)” is turned on or off.
The circuit is normal if the “Malfunction Indicator Lamp
(Check Engine Lamp)” in the instrument panel is turned
on or off in accordance with this operation.
F1: Relays
F0: Fuel Pump Relay
When the Tech 2 is operated, fuel pump relay signal
turns ON or OFF.
The circuit is normal if fuel pump sound is generated in
accordance with this operation when key switch is
turned ON.
F1: A/C Clutch Relay
When the Tech 2 is operated, A/C clutch relay signal
turns ON or OFF.
The circuit is normal if A/C compressor clutch is
energized in accordance with this operation when the
engine is running.
F2: EVAP
F0: Purge Solenoid
When the Tech 2 is operated, duty ratio of EVAP purge
solenoid is changed 10%-by-10%.
• Press “Increase” key. Then, EVAP Purge Solenoid is increases 10%-by-
10%.
• Press “Quit” Key. F3: IAC System
F0: IAC Control
When the Tech 2 is operated, “Idle Air Control”
increases or decreases 5steps-by-5steps up to
150steps.
The circuit is normal if idle engine speed is changed in
accordance with this operation.
• Press “Increase” key. Then, Idle Air Control is increases 1osteps-by-
10steps up to 160steps. Engine speed is also
changed by this operation.
• Press “Quit” Key.
F1: IAC Reset
When the Tech 2 is operated, “Idle Air Control” resets.
The circuit is normal if idle engine speed is droped in
accordance with this operation.
• Press “Increase” key. Then, Desired Idle speed is increases 50rpm-by-
50rpm up to 1550rpm. Engine speed is also changed
by this operation.
• Press “Quit” Key.
Purge Solenoid
Engine Speed 800 RPM
Desired Idle Speed 762 RPM
Engine Coolant Temperature 80 °C
Start Up ECT 50 °C
Intake Air Temperature 30 °C
Start Up IAT 25 °C
Manifold Absolute Pressure 35kPa
EVAP Purge Solenoid 30%
IAC Control
Engine Speed 800 RPM
Desired Idle Speed 762 RPM
Engine Coolant Temperature 80 °C
Sta rt U p E C T 50 °C
Intake Air Temperature 30 °C
Start Up IAT25 °C
Manifold Absolute Pressure 35kPa
Idle Air Control 30 Steps
IAC Reset
Engine Speed 800 RPM
Desired Idle Speed 762 RPM
Engine Coolant Temperature 80 °C
Sta rt U p E C T 50 °C
Intake Air Temperature 30 °C
Start Up IAT 25 °C
Manifold Absolute Pressure 35kPa
Idle Air Control 30 Steps

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ENGINE DRIVEABILITY AND EMISSIONS 6E–77
F4: Injector Balance Test
When the Tech 2 is operated, selected injector turns ON
or OFF.
The circuit is normal if engine vibration is changed at
selected cylinder in accordance with this operation
when engine is idling.
• Press “Injector Off” key. Then, engine speed drops and vibration occurs when
a cylinder is selected.
• Press “Quit” Key. Injector Balance Test
Engine Speed 800 RPM
Desired Idle Speed 762 RPM
Engine Coolant Temperature 80
Start Up ECT 50
Intake Air Temperature 30
Start Up IAT 25
Manifold Absolute Pressure 35kPa
Injector 1 On

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6E–86 ENGINE DRIVEABILITY AND EMISSIONS
5. After choosing the data, click the “Next” button.
6. When all the necessary information is entered, the “details” of software within the database that match
the entered data will appear for confirmation. Click
the “Program” switch and then download the new
software onto Tech-2.
7. “Data Transfer” comes on display. The progress of downloading will be displayed on the screen in the
form of bar graph.
8. Upon finishing the data transfer, turn off the power of Tech-2, removing from P/C. 4. Programming of ECM
1. Check to see if batteries are fully charged, while ABS connectors shall be removed from the vehicle.
2. Connect Tech-2 to Vehicle Diagnostic Connectors.
3. Turn on the power of Tech-2 and the title screen comes on display.
4. Turn on the ignition (without allowing the engine to start)
5. On the title screen of Tech-2, push the “Enter” button.
6. Choose “F1: Service Programming System” on the main screen and then choose “Fl: Program ECU”.
7. While data is being transferred, “Programming in Progress” will be displayed on the Tech-2 screen.
8. Upon finishing the data transfer, Tech-2 will display “Reprogramming Was Successful”. Push the “Exit”
button to bring program to completion
9. Following “Procedure 2: Demand of Data”, try over again “Information Obtaining” and check to confirm
if the data has been correctly re-loaded.
10. Upon finishing confirmation, turn off the ignition of the vehicle and then turn off the power of Tech-2,
removing from the vehicle.

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6E–98 ENGINE DRIVEABILITY AND EMISSIONS
FUEL METERING SYSTEM CHECK
Some failures of the fuel metering system will result in
an “Engine Cranks But Will Not Run” symptom. If this
condition exists, refer to the Cranks But Will Not Run
chart. This chart will determine if the problem is caused
by the ignition system, the ECM, or the fuel pump
electrical circuit.
Refer to Fuel System Electrical Test for the fuel system
wiring schematic.
If there is a fuel delivery problem, refer to Fuel System
Diagnosis , which diagnoses the fuel injectors, the fuel
pressure regulator, and the fuel pump.
Followings are applicable to the vehicles with
closed Loop System:
If a malfunction occurs in the fuel metering system, it
usually results in either a rich HO2S signal or a lean
HO2S signal. This condition is indicated by the HO2S
voltage, which causes the ECM to change the fuel
calculation (fuel injector pulse width) based on the
HO2S reading. Changes made to the fuel calculation
will be indicated by a change in the long term fuel trim
values which can be monitored with a Scan Tool. Ideal
long term fuel trim values are around 0%; for a lean
HO2S signal, the ECM will add fuel, resulting in a fuel
trim value above 0%. Some variations in fuel trim values
are normal because all engines are not exactly the
same. If the evaporative emission canister purge is 02
status may be rich condition. 02 status indicates the
lean condition, refer to DTC P1171 for items which can
cause a lean HO2S signal.
FUEL INJECTOR COIL TEST PROCEDURE
AND FUEL INJECTOR BALANCE TEST
PROCEDURE
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart:
2. Relieve the fuel pressure by connecting 5-8840- 0378-0 T-Joint to the fuel pressure connection on the
fuel rail.
Caution: In order to reduce the risk of fire and
personal injury, wrap a shop towel around the
fuel pressure connection. The towel will absorb
any fuel leakage that occurs during the
connection of the fuel pressure gauge. Place the
towel in an approved container when the
connection of the fuel pressure gauge is
complete.
Place the fuel pressure gauge bleed hose in an
approved gasoline container.
With the ignition switch OFF open the valve on the
fuel pressure gauge.
3. Record the lowest voltage displayed by the DVM after the first second of the test. (During the first
second, voltage displayed by the DVM may be
inaccurate due to the initial current surge.)
Injector Specifications:
• The voltage displayed by the DVM should be within the specified range.
• The voltage displayed by the DVM may increase throughout the test as the fuel injector windings
warm and the resistance of the fuel injector
windings changes. Resistance Ohms
Voltage Specification at
10°C-35°C (50°F-95°F)
11.8-12.6 5.7-6.6

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ENGINE DRIVEABILITY AND EMISSIONS 6E–101
5 1. Set the Injector Adapter Cable to injector #1.2. Press the “Push to Start Test” button on the fuelinjector tester.
3. Observe the voltage reading on the DVM.
Important: The voltage reading may rise during the
test.
4. Record the lowest voltage observed after the first second of the test.
5. Set the Injector Adapter Cable to the next injector and repeat steps 2, 3, and 4.
Did any fuel injector have an erratic voltage reading
(large fluctuations in voltage that did not stabilize) or a
voltage reading above the specified value? 9.5V Go to Step 4Go to Step 6
6 1. Identify the highest voltage reading recorded (other than those above 9.5V).
2. Subtract the voltage reading of each injector from the highest voltage selected in step 1. Repeat until
you have a subtracted value for each injector.
For any injector, is the subtracted value in step 2
greater than the specified value? 0.6V Go to Step 4Go to Step 7
7 Caution: In order to reduce the risk of fire and
personal injury, wrap a shop towel around the fuel
pressure connection. The towel will absorb any
fuel leakage that occurs during the connection of
the fuel pressure gauge. Place the Towel in an
approved container when the connection of the
fuel pressure gauge is complete.
1. Connect the 5-8840-0378-0 Fuel Pressure Gauge to the fuel pressure test port.
2. Energize the fuel pump using the Scan Tool.
3. Place the bleed hose of the fuel pressure gauge into an approved gasoline container.
4. Bleed the air out of the fuel pressure gauge.
5. With the fuel pump running, observe the reading on the fuel pressure gauge.
Is the fuel pressure within the specified values? 296kPa-
376kPa
(43-55psi) Go to Step 8Go to
Fuel
System
Diagnosis
8 Turn the fuel pump OFF. Does the fuel pressure remain constant? —Go to Step 9Go to
Fuel
System
Diagnosis
Step
Action Value(s) Yes No

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6E–108 ENGINE DRIVEABILITY AND EMISSIONS
FUEL SYSTEM DIAGNOSIS
Circuit Description
When the ignition switch is turned ON, the engine
control module (ECM) will turn ON the in-tank fuel
pump. The in-tank fuel pump will remain ON as long as
the engine is cranking or running and the ECM is
receiving 58X crankshaft position pulses. If there are no
58X crankshaft position pulses, the ECM will turn the in-
tank fuel pump OFF 2 seconds after the ignition switch
is turned ON or 2 seconds after the engine stops
running.
The in-tank fuel pump is an electric pump within an
integral reservoir. The in-tank fuel pump supplies fuel
through an in-line fuel filter to the fuel rail assembly. The
fuel pump is designed to provide fuel at a pressure
above the pressure needed by the fuel injectors. A fuel
pressure regulator, attached to the fuel rail, keeps the
fuel available to the fuel injectors at a regulated
pressure. Unused fuel is returned to the fuel tank by a
separate fuel return line.
Te s t D e s c r i p t i o n
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. Connect the fuel pressure gauge to the fuel feed line as shown in the fuel system illustration. Wrap a shop
towel around the fuel pressure connection in order to
absorb any duel leakage that may occur when
installing the fuel pressure gauge. With the ignition
switch ON and the fuel pump running, the fuel
pressure indicated by the fuel pressure gauge
should be 283-376 kPa (41-55 psi). This pressure is
controlled by the amount of pressure the spring
inside the fuel pressure regulator can provide.
3. A fuel system that cannot maintain a constant fuel pressure has a leak in one or more of the following
areas:
• The fuel pump check valve.
• The fuel pump flex line.
• The valve or valve seat within the fuel pressure regulator.

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