Page 217 of 4770
Fuel pumped up by the fuel pump, flows through the fuel filter and is distributed to each injector
at a set pressure maintained by the pressure regulator.
The fuel pressure regulator adjusts the pressure of the fuel from the fuel line (high pressure side)
to a pressure 284 kPa (2.9 kgf/cm, 41 psi) higher than the pressure inside the cylinder head, and
excess fuel is returned to the fuel tank through the return pipe.
The pulsation damper absorbs the slight fluctuations in fuel pressure caused by fuel injector from
the injector.
The injectors operate on input of injection signals from the ECM and inject fuel into the cylinder
head.
OPERATION
FUEL SYSTEM
± 5S±FE ENGINEMFI/SFI SYSTEMEG1±167
Page 218 of 4770
Air is filtered through the air cleaner and the amount flowing to the air intake chamber is
determined according to the throttle valve opening in the throttle body and the engine speed.
Intake air controlled by the throttle valve opening is distributed from the air intake chamber to the
manifold of each cylinder and is drawn into the combustion chamber.
At low temperatures the IAC valve opens and the air flows through the IAC valve and the throttle
body, into the air intake chamber. During engine warming up, even if the throttle valve is
completely closed, air flows to the air intake chamber, thereby increasing the idle speed (first idle
operation).
The air intake chamber prevents pulsation of the intake air. It also prevents intake air interference
in each cylinder.
AIR INDUCTION SYSTEM
± 5S±FE ENGINEMFI/SFI SYSTEMEG1±168
Page 219 of 4770
The control system consists of sensors which detect various engine conditions, and a ECM which
determines the injection volume (timing) based on the signals from the sensors.
The various sensors detect the intake air pressure, engine speed, oxygen density in the exhaust
gas, engine coolant temperature, intake air temperature and atmospheric pressure etc. and
convert the information into an electrical signal which. is sent to the ECM. Based on these signals,
the ECM calculates the optimum ignition timing for the current conditions and operates the
injectors.
The ECM not only controls the fuel injection timing, but also the self diagnostic function which
records the occurrence of a malfunction, ignition timing control, idle speed control and EGR
control.
ELECTRONIC CONTROL SYSTEM
± 5S±FE ENGINEMFI/SFI SYSTEMEG1±169
Page 220 of 4770
PREPARATION
SST (SPECIAL SERVICE TOOLS)
(90405±09015) No.1 Union (09268±41090) No.7 union (09268±41080) No.6 union
09631±22020 Power Steering Hose Nut
14 x 17 mm Wrench Set
RECOMMENDED TOOLS
Plug for vacuum hose, fuel hose
etc. 09268±41045 Injection Measuring Tool Set
09082±00050 TOYOTA Electrical Tester Set 09842±30070 Wiring ªFº EFI Inspection 09268±45012 EFI Fuel Pressure Gauge
09843±18020 Diagnosis Check Wire
09200±00010 Engine Adjust Kit
09258±00030 Hose Plug SetFuel line flare nut
± 5S±FE ENGINEMFI/SFI SYSTEMEG1±170
Page 221 of 4770
EQUIPMENT
Graduated cylinderCarburetor cleaner
Vacuum gauge Torque wrenchSound scopeThrottle body
TachometerThrottle body
Soft brush
InjectorInjector
± 5S±FE ENGINEMFI/SFI SYSTEMEG1±171
Page 222 of 4770

PRECAUTION
1. Before working on the fuel system, disconnect the
negative (±) terminal cable from the battery.
HINT: Any diagnostic trouble code retained by the
computer will be erased when the battery terminal is
removed.
Therefore, if necessary, read the diagnosis before
removing the terminal.
CAUTION: Work must be started after 90 seconds from
the time the ignition switch is turned to the 'LOCK'
position and the negative (±) terminal cable is discon±
nected from the battery.
2. Do not smoke or work near an open flame when
working on the fuel system.
3. Keep gasoline away from rubber or leather parts.
3. IN EVENT OF ENGINE MISFIRE, FOLLOWING
PRECAUTIONS SHOULD BE TAKEN
(a) Check proper connection of battery terminals, etc.
(b) Handle high±tension cords carefully.
(c) After repair work, check that the ignition coil termi±
nals and all other ignition system lines are reconne±
cted securely.
(d) When cleaning the engine compartment, be especially
careful to protect the electrical system from water.
4. PRECAUTIONS WHEN HANDLING OXYGEN
SENSOR
(a) Do not allow oxygen sensor to drop or hit against an
object.
(b) Do not allow the sensor to come into contact with
water.
MAINTENANCE PRECAUTIONS
1. CHECK CORRECT ENGINE TUNE±UP
(See page EG1±8)
2. PRECAUTION WHEN CONNECTING GAUGE
(a) Use battery as the power source for the timing light,
tachometer, etc.
(b) Connect the tester probe of a tachometer to the termi±
nal IGE) of the data link connector 1.
± 5S±FE ENGINEMFI/SFI SYSTEMEG1±172
Page 223 of 4770

ELECTRONIC CONTROL SYSTEM
1. Before removing MFI/SFI wiring connectors, termi±
nals, etc., first disconnect the power by either turning
the ignition switch OFF or disconnecting the battery
terminals.
HINT: Always check the diagnostic trouble code
before disconnecting the negative (±) terminal cable
from the battery.
2. When installing the battery, be especially careful not
to incorrectly connect the positive (+) and negative
(±) cables.
3. Do not permit parts to receive a severe impact during
removal or installation. Handle all MFI/SFI parts care±
fully, especially the ECM.
4. Do not be careless during troubleshooting as there are
numerous transistor circuits and even slight terminal
contact can further troubles.
5. Do not open the ECM cover.
6. When inspecting during rainy weather, take care to
prevent entry of water. Also, when washing the
engine compartment, prevent water from getting on
the MFI/SFI parts and wiring connectors.
7. Parts should be replaced as an assembly.
AIR INDUCTION SYSTEM
1. Separation of the engine oil dipstick, oil filler cap, PCV
hose, etc. may cause the engine to run out of tune.
2. Disconnection, looseness or cracks in the parts of the
air induction system between the throttle body and
cylinder head will allow air suction and cause the
engine to run out of tune.
IF VEHICLE IS EQUIPPED WITH MOBILE
RADIO SYSTEM (HAM, CB, ETC.)
If the vehicle is equipped with a mobile communica±
tion system, refer to the precaution in the IN section.
± 5S±FE ENGINEMFI/SFI SYSTEMEG1±173
Page 224 of 4770
(b) Insert the test probe into the connector from wiring
side when checking the continuity, amperage or volt±
age.
(c) Do not apply unnecessary force to the terminal.
(d) After checking, install the water±proofing rubber on
the connector securely. 8. Care is required when pulling out and inserting wiring
connectors.
(a) Release the lock and pull out the connector, pulling on
the connectors.
9. When inspecting a connector with a volt/ohmmeter.
(a) Carefully take out the water±proofing rubber if it is a
water±proof type connector.
10. Use SST for inspection or test of the injector or its
wiring connector.
SST 09842±30070 (b) Fully insert the connector and check that it is locked.
± 5S±FE ENGINEMFI/SFI SYSTEMEG1±174