check engine MITSUBISHI ECLIPSE 1991 Service Manual

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.

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
<I .8L Engine>l TDC sensor, crank angle sensor<2.0L DOHC Engine>
l Power steering oil pressure switch
l Air conditioner switch
l Inhibitor switch <A/T>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.

14-8FUEL SYSTEM - Troubleshootingiymptom
<ough idle or engine
#table
Probable causeMalfunction
of the vehicle speed reed switch
Remedy
Check the vehicle speed reed switch.
The fuel pressure is not proper.Check the fuel pressure.
Vacuum hose disconnected or damaged.Repair or replace.Malfunction
of the engine control unit.Replace.
Wire breakage or short circuit occurs in theRepair or replace.
harness, or the connector is improperly connected.
.ngine hesrtates oroor accelerationTrouble in the MPI systemCheck for output of self-diagnosiscode.Read the code with a voltmeter.
Malfunction of the sensorl Intake air temperature sensor
l Engine coolant temperature sensor
l Barometric pressure sensorl Ignition switch
l Idle position switchl Throttle position sensor
Check the sensor-related circuit.Check the sensor as a single unit.l
No. 1 cylinder TDC sensor, crank angle sensor<I .8L Engine>
l TDC sensor, crank angle sensor<2.0L DOHC Engine>
l Power steering oil pressure switchl Air conditioner switchl Inhibitor switch <A/T>l Motor position sensor <I .8L Engine>
l Air flow sensor
l Oxygen sensorMalfunction
of the engine control system
l
Stepper motor <2.0L DOHC Engine>
0 Injector0 Power transistor
Check the actuator-related circuit.
Check the actuator as a single unit.Malfunction
of the air conditioner power relayCheck the system, and the compo-
control systemnents if the system is found defective.
The fuel pressure is not proper.Check the fuel pressure.
Vacuum hose disconnected or damaged.Repair or replace.Malfunction
of the engine control unit.Replace.
Wrre breakage or short circuit occurs in theRepair or replace.
harness, or the connector is improperly connected.

FUEL SYSTEM - Troubleshooting14-S
Symptom
Poor fuel mileage,
Probable cause
Trouble In the MPI system
Remedy
Check for output of self-diagnosis
code.Read the code with a voltmeter.Malfunction
of the sensorl Intake air temperature sensorl Engine coolant temperature sensorl Barometric pressure sensorl Ignition switchl Idle position switch
l Throttle position sensorl No. 1 cylinder TDC sensor, crank angle sensor
Check the sensor-related circuit.Check the sensor as a single unit.
<I .8L Engine>l TDC sensor, crank angle sensor<2.0L DOHC Engine>
l Power steering oil pressure switch
l Air conditioner switch
l lnhrbrtor switch <A/T>l Motor
position sensor <I .8L Engine>
l Air flow sensor
0 Oxygen sensor
Malfunction of the engine control system
l Stepper motor <2.0L DOHC Engine>
0 Injector0 Power transistor
Check the actuator-related circurt.Check the actuator as a single unit.
The fuel pressure is not proper.Check the fuel pressure.

FUEL SYSTEM - Service Adjustment Procedures <1.8L Engine>l-4-41
SERVICE ADJUSTMENT PROCEDURES
<I .8L Engine>
CURB IDLE SPEED INSPECTION
CautionNlIFiiAE
The improper setting (throttle valve opening) will increase
exhaust gas temperature at deceleration, reducing catalystlife greatly and deteriorating exhaust gas cleaning per-
formance. It also has effect on fuel consumption and
engine braking.
ilter
Paper clip
16A0898
PI-e-conditions for inspection
0Engine coolant temperature: 85-95°C (185-205°F)
0Lights, electric cooling fan and accessories: OFF
l Transaxle: Neutral
(P for vehicles with an automatic
transaxle)l Steering wheel: Neutral position (vehicles with a power
steering)l Check ignition timing and adjust if necessary. Refer to
GROUP 8.
NOTEWith vehicles for Canada, the headlights and taillights, etc.
remain on even when the lighting switch is turned OFF, but thiscauses no problems during inspection.
(1) Insert the paper clip to the connector.
(2) Connect the tachometer to the inserted clip.
(3)Run the engine for more than 5 seconds at an engine speedof 2,000 to 3,000 rpm.
(4) Run the engine at idle for 2 minutes.
(5) Read the idling rpm. If it is not within the specified speed,
check the idle speed control system.
Curb idle speed: 700
f 100 rpm
NOTEAdjustment of the idling speed is usually unnecessary,
because this system controls the idling speed.
IDLE SPEED CONTROL AND
THROTlLE POSI-
TION SENSOR ADJUSTMENT
N14FIATAdjustment conditions
l Engine coolant temperature:
85-95X (185-205°F)
l Lights, electric cooling fan and accessories: Set to OFF
l Transaxle: Neutral (P for vehicles with an automatic
transaxle)l Steering wheel: Neutral position (vehicles with a power
steering)
(1) Slacken the accelerator cable enough.
(2) Connect a tachometer.

14-42FUEL SYSTEM - Service Adjustment Procedures C1.8L Engine>
6FU13%
Idle speed control
adjusting screw(3) Connect a digital voltmeter between terminal 19 (throttle
position sensor output voltage) of the engine control unit
kand terminal 24 (ground).
(4) Set the ignition switch at ON (without starting the engine)
hold it in that position for more than 15 seconds or more.
(5) Set the ignition switch at OFF.
(6) Disconnect the connectors of the idle speed control servo
and lock the idle speed control plunger at the initial position.(7) Back out the fixed SAS enough.
(8) Start the engine and let it run at idle.
(9) Check to ensure that the engine is running at the standard
basic idle speed.
Basic idle speed:
700&50 rpm
CautionLr1. On a new vehicle [driven less than 500 km
(380miles)], the engine speed may ‘be 20 to
100 rpm
lower, but no adjustment is necessary.
2.If the engine stalls or the engine speed is low after
the vehicle has been driven a distance of 500 km
(300 miles) or more, a deposit on the throttle valve
area is suspected. Clean the throttle valve area.
(10)lf the engine speed does not conform to the standard
value, adjust it with the idle speed control adjusting screw.
Caution
When adjusting the idle speed control, use a hexagon
wrench whenever possible.
(11)Turn in the fixed SAS .until the engine speed rises. Then
back out the fixed SAS until the “touch point” where the
engine speed does not fall any longer is found. Back out thefixed SAS an additional half a turn from the touch point.
(12)Stop the engine.
(13)Set the ignition switch at ON (do not start the engine) and
check that the output voltage from the throttle position
sensor is as specified.
Standard value:
0.48-0.52 VA

FUEL SYSTEM - Service Adjustment Procedures <1.8L Engine>14-43
(14)lf it is out of specification, adjust by loosing the throttle
position sensor mounting screws and rotating the throttle
position sensor. After adjustment, tighten the screws
firmly.
NOTEClockwise rotation of the throttle position sensor increases
the output voltage.
Throttle position
sensor
t-/ /I
(15)Set the ignition switch at OFF.
(16)Adjust the free play of the accelerator cable.
(17)Reconnect the connectors of the idle speed control servo.
(18)Remove the voltmeter.
(19)Start the engine and check that the engine is running at thecurb idle speed.
Curb idle speed:
700f 100 rpm
(20)Set the ignition switch at OFF, disconnect the negative
battery cable and reconnect it more than
10 seconds later
(By doing so, the memory storing the diagnosis data duringthe idle speed control adjustment is cleared.)
(21)Restart the engine, let it run at idle for about 5 minutes, andcheck that the engine is running in good idle quality.
THROTTLE BODY (THROTTLE VALVE AREA)
CLEANING
NllRCK
(1) Warm up the engine, then stop it.
(2) Remove the air intake hose from the throttle body.
(3) Spray cleaning solvent into the valve through the throttle
body intake port and leave it for about 5 minutes.
(4) Start the engine, race it several times and idle it for about 1minute. If the idling speed becomes unstable slightly open
the throttle valve to keep the engine running.
(5) If the throttle valve deposits are not removed, repeat steps
(3) and (4).
(6) Attach the air intake hose.
(7) Disconnect the battery terminal for
10 seconds or more,
and then reconnect it.
(8) Adjust the idle speed control and throttle position sensor.

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.
-

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.

14-46FUEL SYSTEM - Service Adjustment Procedures <1.8L Engine>
Condition
Fuel pressure too low
Fuel pressure too highProbable causea. Clogged fuel filter
b. Fuel leaking toward return port due to
Remedy
a. Replace fuel filter.
improper seating of valve in fuel pressure
b. Replace fuel pressure regulator.
regulatorc. Low delivery pressure of fuel pump
c. Replace fuel pump.
a. Stuck valve in fuel pressurea. Replace fuel pressure regulator.
regulator
b. Clogged or bent fuel return hose or pipeb. Repair or replace hose or pipe.
‘.
Fuel pressure witha. Clogged or broken vacuum hose or nipple
a. Repair or replace the vacuum hose or
vacuum hose connectednipple.
not different from fuel
pressure with vacuum
b. Stuck valve in fuel pressure regulator orb. Replace fuel pressure regulator.
hose not connecteddefective valve seating
(13)Stop the engine and check for change in fuel pressure
gauge indication, which should not drop.
If the gauge indication drops, observe the rate of drop and
determine and remove the causes according to the
following table.
ConditionProbable causeRemedy
Fuel pressure dropsLeakage from injectorReplace injector.
slowly after engine is
stopped.
rqFuel pressure drops im-Check valve in fuel pump does not closeReplace fuel pump.
mediately after engine is
stooped.
(14)Reduce the fuel pressure in the fuel line.
(16)Disconnect the high pressure fuel hose and remove the
fuel pressure gauge from the delivery pipe.
Caution
Cover the hose connection with shop tdwel to prevent
splash of fuel that could be caused by residual pressure
in the fuel pipe line.
(16)Mount a new O-ring in the groove at the end of the high
pressure fuel hose.
(17)Connect the high pressure fuel hose to the delivery pipe,
and tighten the screws to the specified torque.
(18)Check for fuel leaks.
@ Apply battery voltage to the fuel pump check terminal
to operate the fuel pump.
@ With fuel pressure acting, check the fuel line for leaks.
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