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14-6FUEL SYSTEM - Special Tools/Troubleshooting
SPECIAL TOOLSNWA-B
Number
M D998742
Name
Hose adapter
Usel Measurement
of fuel pressure (to be usedtogether
with MD9987091
MD998709Adapter hosel Measurement of fuel pressure (to be usedtogether
with MD9987421
TROUBLESHOOTING
When checking and correcting engine troubles, it is
important to start with inspection of the basic
systems.
In case you have such troubles as (1) engine start
failure, (2) rough idling or (3) poor acceleration,
therefore, you should first check the following basic
systems:
(1) Power supply
0 Batteryl
Fusible linkl
Fuse
(2) Body ground
(3) Fuel supplyl
Fuel linel
Fuel filter
l
Fuel pump
N14EBBH
(4) Ignition systeml
Spark plugsl
High tension cablel Distributor
<1.8L Engine>
l
Crank angle sensor <2.0L DOHC Engine>
0 Ignition coil
(5) Emission control systeml
Crankcase ventilation systeml
Exhaust gas recirculation systeml
Vacuum leak
(6) Others
0 Ignition timing
l
Idle speed
Troubles with the MPI system are often caused by
poor contact of harness connector. It is, therefore,
important to check harness connector contact.
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FUEL SYSTEM - Troubleshooting14-7
Symptom
Engine will not startor start too hard(Cranks OK)
Rough idle or engine
stumbles
Trouble in the MPI systemCheck for output of self-diagnosis
code.Read the code with a voltmeter.Malfunction
of the fuel pump drive control systemCheck the fuel pump drive controlsystem
and the fuel pump.Malfunction
of the ignition timing control systemMalfunction
of the power transistor
Check the ignition timing.
Check the power transistor as a single
unit.
Power is not supplied to the engine control unit.Check the power supply circuit.Malfunction
of the control relayMalfunction
of the injector
Replace.
Check the injector drive circuit.
Check the injector as a single unit.
The fuel pressure is not proper.Check the fuel pressure.
I
Vacuum hose disconnected or damagedRepair or replace.IMalfunction of
the engine control unit) Replace.
Wire breakage or short circuit occurs in theRepair or replace.
harness, or the connector is improperly connected.
Trouble in the MPI systemCheck for output of self-diagnosis
code.Read the code with a voltmeter.Malfunction
of the sensor
l Intake air temperature sensor
Check the sensor-related circuit.
Check the sensor as a single unit
Probable causeRemedy
l Engine coolant temperature sensorl Barometric pressure sensor
l Ignition switchl Idle position switchl Throttle position sensorl No. 1 cylinder TDC sensor, crank angle sensor
l TDC sensor, crank angle sensor<2.0L DOHC Engine>
l Power steering oil pressure switch
l Air conditioner switch
l Inhibitor switch l Motor position sensor <1.8L Engine>l Air flow sensor0 Oxygen sensorMalfunction of the engine control system
l
Stepper motor <2.0L DOHC Engine>l Injector0 Power transistor
Check the actuator-related circuit.Check the actuator as a single unit.
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CONTROL FUNCTIONS
<1.8L Engine>
NWEEE- -
FunctionAir-fuelIgnitionIdleAir con-FuelPurgeEGRmixture
timingspeedditionercontrol
controlcontrolpower“d”,i2controlcontrol
relaycontrol
Functional elements
control
In-Power supplyXXXXXXX
Put(Ignition switch coupled)
Power supply (battery backup)
XXXXXXXAir flow sensor
XXXX
lgnitron switch ST terminalXXX(start srgnal)Power
steenng oil pressure switchX
Jut- InjectorXlutIdle speed control servoXPower transistor
X
Arr conditioner power relayX
Control relayX
Purge control solenord valveX
EGR control solenoid valveX
NOTE*:
FUEL SYSTEM - Troubleshooting
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Page 498 of 1216
FUEL SYSTEM - Service Adjustment Procedures 4.8L Engine>
RELEASE OF RESIDUAL
PRESSURE FROM HIGHPRESSURE FUEL HOSE
N14FGAE
MD998709
MD998742
IFUO157Make the following operations to release the pressure remain-
ing in fuel pipe line so that fuel will not flow out.
(1) Disconnect the fuel pump harness connector at the fuel
tank rear side.
(2) Start the engine and after it stops by itself, turn the ignition
switch to OFF.
(3) Disconnect the battery
(-) terminal.
(4) Connect the fuel pump harness connector.
FUEL PUMP OPERATION CHECK
Nl4FDAG(1) Set the ignition switch at OFF.
(2) Check that when the batten/ voltage is directly applied to
the fuel pump check terminal, the operating sound of the
pump can be heard.
NOTESince the fuel pump is installed in the fuel tank, its
operating sound cannot be readily heard. Remove the fuel
tank cap and listen to the operating sound through the filler
port.(3) Hold the high pressure fuel hose between your fingers and
check that the fuel pressure can be felt.
FUEL PRESSURE TEST
Nl4FNAN(1) Reduce the fuel pressure in the fuel line.
(2) Disconnect the high pressure fuel hose from the delivery
pipe.
CautionCover the hose connection with shop towel to prevent
splash of fuel that could be caused by residual pressurein the fuel pipe line.
(3) Connect a fuel pressure gauge to the special tool (hose
adapter).Use a suitable O-ring or gasket between the fuel pressure
gauge and the special tool so as to seal in order to preventfuel leakage at this time.
-
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FUEL SYSTEM - Service Adjustment Procedures 4.8L Engine>14-45(4) Install the special tool, which was set in place in step
(3),
between the delivery pipe and the high pressure fuel hose.(5) Connect the
0 terminal of the batten/.
(6) Apply battery voltage to the fuel pump check terminal and
activate the fuel pump; then, with fuel pressure thus
applied, check to be sure that there is no fuel leakage fromthe pressure gauge or the special tool connection part.
(7) Start the engine and run at curb idle speed.
(8) Disconnect the vacuum hose form the pressure regulator
and clog the vacuum hose end. Measure the fuel pressure.Standard value:
330-350 kPa (47-50 psi) at curb idle
(9) Measure the fuel pressure when the vacuum hose is
connected to the pressure regulator:
Standard value: Approx. 270
kPa (38 psi) at curb idle
(10)Race the engine repeatedly in two or three series. Then
check that the fuel pressure does not fall when the engine
is running at idle.
(11)Check to be sure that there is fuel pressure in the return
hose also (by gently pressing the fuel return hose with a
finger while repeatedly racing the engine).
NOTEThere will be no fuel pressure in the return hose when the
volume of fuel flow is not sufficient.
(12)lf the results of the measurements made in steps (8) and
(9) above are not within the standard value, use the table
below to determine the probable cause, and then make the
necessan/ repair.
