water MAZDA 626 1987 Workshop Manual

4C FUEL SYSTEM
COMPONENT DESCRIPTION
Component Function Remark
Air flow sensor Detects amount of intake air;
sends signal to engine control unit
Clutch switch Detects in-gear condition; sends signal to engine control unit Switch ON when clutch pedal released
Engine control unit Detects signals from input sensors and switches; controls injector and fuel pump operations
Fuel filter Filters fuel
Fuel pump Provides fuel to injectors • Operates while engine running
• Installed in fuel tank
Fuel pump control unit (4WS) Monitors fuel level in left section; controls transfer pump operation
G signal pick-up Detects No.1 cylinder TDC; sends signal to engine control unit Installed in distributor
Idle switch Detects when throttle valve fully closed; sends signal to engine control unit Installed on throttle body
Ignition switch (ST position) Sends engine cranking signal to engine control unit
Injector Injects fuel into intake port • Controlled by signals from engine control unit • High-ohmic injector
Intake air thermo sensor Detects intake air temperature; send signal to engine control unit
Control relay Supplies electric current to injectors fuel pump and engine control unit
Ne signal pick-up Detects crank angle at 180° intervals; sends signal to engine control unit Installed in distributor
Neutral switch Detects in-gear condition; sends signal to engine control unit
Switch ON when in gear
Oxygen sensor (Unleaded fuel) Detects oxygen concentration; sends signal to engine control unit
• Zirconia ceramic and platinum coating • Integrated heater coil
Pressure regulator Adjusts fuel pressure supplied to injectors
Pulsation damper Absorbs fuel pulsation
Throttle sensor Detects throttle valve opening angle;
sends signal to engine control unit
Installed on throttle body
Transfer pump (4WS) Pumps fuel from the left to the right side Controlled by fuel pump control unit
Transfer pump switch (4WS) Detects fuel level in left section;
sends signal to control unit
Water thermo sensor Detects coolant temperature; sends signal to engine control unit
Water thermo switch (Unleaded fuel) Detects radiator coolant temperature; sends signal to engine control unit ON: above 17°C (63°F)
76G04C-088
4C-50

PRC SYSTEM 4C
COMPONENT DESCRIPTION
Component Function Remark
Engine control unit Detects signals from input sensors and switches; con-trols solenoid valve (Pressure regulator control)
Ignition switch
(ST position)
Sends engine cranking signal to engine control unit
Intake air thermo sensor Detects intake air temperature; sends signal to engine control unit
Ne signal pick-up Detects crank angle at 180° intervals; sends signal to engine control unit Installed in distributor
Pressure regulator Adjusts fuel pressure supplied to injectors
Solenoid valve (Pres-
sure regulator control)
Controls vacuum to pressure regulator Cuts vacuum when hot
Water thermo sensor Detects coolant temperature; sends signal to engine control unit
Idle switch Detects when throttle valve closed; sends signal to engine control unit ON at idle
76G04C-129
TROUBLESHOOTING
Check the condition of the wiring harness and connections before checking the sensors or switches.
Note
Make the system inspection first. If no problem is found, continue with inspection of the
next system of the Troubleshooting Guide. (Refer to pages 4C—10 and 11.)
Possible
\ cause
\ Page
Solenoid valve (Pres-sure regula-tor control)
Water thermo
sensor
Intake air
thermo
sensor
Engine con-trol unit terminal
System inspection Solenoid valve (Pres-sure regula-tor control) 2K
Symplon 4C—70 4C—107 4C-110 4C—98 4C—70
Engine stalls or runs rough after hot starting 2 3 4 5 1
76G04C-130
4C-69

4C PRC SYSTEM
System Inspection
1. Connect the SST to the engine. (Refer to page
4C-53.)
2. Start the engine.
76G04C-131
Hi?
Jpll ssil
Water thermo sensor ^^^Tta^e air thermo sensor
76G04C-132
Operating time Fuel line pressure kPa (kg/cm2, psi)
After starting: for 120 sec. 235-275 (2.4-2.8, 34-40)
After 120 sec. 186-226 (1.9-2.3, 27-33)
3. Warm up the engine to normal operating temper-
ature and stop the engine.
Warning
Be careful when disconnecting the water ther-
mo sensor connector because the surround-
ing area is very hot.
4. Disconnect the water thermo sensor connector.
Connect a resistor (200 fl) to the sensor connector.
5. Heat the intake air thermo sensor to above specifi-
cation.
Specification: 30°C (86°F)....unleaded fuel
50°C (122°F)....leaded fuel
6. Restart the engine.
7. Check the fuel line pressure and operating times
as shown in the chart.
76G04C-133
Solenoid Valve (Pressure Regulator Control)
Inspection
1. Disconnect the vacuum hose from the vacuum
pipe.
2. Blow through the solenoid valve from vacuum hose
A.
3. Check that air flows from port B.
76G04C-134
4C—70

4C DECELERATION CONTROL SYSTEM
DECELERATION CONTROL SYSTEM
Distributor
(Ne signal)
Idle switch
QSO-Water thermo sensor
=5
A/C switch
Engine control unit
Detection of
fuel cut
condition Determi-
nation of
fuel cut
speed
* *
1
T
No.3

I
No.4
No.2
The fuel cut system is provided as a deceleration control system.
This system is to improve fuel consumption.
86U04A-121
4C—72

DECELERATION CONTROL SYSTEM 4C
COMPONENT DESCRIPTION
Component Function Remarks
Engine control unit Detects signals from input sensors and switches; cuts fuel injection
Idle switch Detects when throttle valve fully closed; sends signal to engine control unit ON at idle
Ne signal pick-up Detects crank angle at 180° intervals; sends signal to engine control unit Installed in distributor
Water thermo sensor Detects coolant temperature; sends signal to engine control unit
76G04C-135
TROUBLESHOOTING
Check the condition of the wiring harness and connectors before checking the sensor or switches.
Note
Make the system inspection first. If no problem is found, continue with inspection of the
next system of the Troubleshooting Guide. (Refer to page 4C—10 and 11.)
Possible cause Water thermo sensor System inspection
Page 4C—107 4C—74
Checking order 2 1
76G04C-136
4C-73

EGR SYSTEM (UNLEADED FUEL) 4C
EXHAUST GAS RECIRCULATION
(EGR)
SYSTEM (UNLEADED FUEL)
This system introduces exhaust gas into the intake manifold to reduce NOx emissions. It operates de-
pending on the engine load, engine speed (1,500—3,500 rpm), engine coolant temperature (above
70°C, 158°F), and radiator coolant temperature (above 17°C, 63°F).
COMPONENT DESCRIPTION
Component Function Remark
EGR control valve Recirculates portion of exhaust gas
EGR modulator valve Controls vacuum acting on EGR control valve
Engine control unit Detects signals from input sensors and switches; con-trols solenoid valve (EGR)
Ne signal pick-up Detects crank angle at 180° intervals; sends signal to engine control unit
Solenoid valve (EGR) Controls vacuum to EGR control valve
Throttle sensor Detects throttle valve opening angle; sends signal to en-
gine control unit
Installed on throttle body
Water thermo sensor Detects coolant temperature; sends signal to engine control unit
Water thermo switch Detects radiator coolant temperature; sends signal to engine control unit ON: above 17°C (63°F)
76G04C-143
AC—17

4C EGR SYSTEM (UNLEADED FUEL)
TROUBLESHOOTING
Check the condition of the wiring harness and connectors before checking the sensors or switches.
Note
Make the system inspection first. If no problem is found, continue with inspection of the
next system of the Troubleshooting Guide. (Refer to pages 4C—10 and 11.)
Possible cause
Throttle
sensor
Solenoid valve
(EGR)
EGR
modula-
tor valve
EGR con-trol valve
Water
thermo
sensor
Water
thermo switch
Engine control unit
terminal
System in-spection
2N
Page 4C—104 4C—78 4C—79 4C—79 4C—107 4C—106 4C—98 4C—78
Checking order 8 2 4 3 6 5 7 1
76G04C-144
System Inspection
1. Start the engine.
2. Accelerate the engine while still cold and verify that
the diaphragm of the EGR control valve does not
move.
3. Warm up the engine to normal operating temper-
ature and run it at idle.
Warning
Be careful when checking the EGR control
valve, the surrounding area is very hot.
4. Accelerate the engine and check that the di-
aphragm of the EGR control valve moves.
Solenoid Valve (EGR)
1. Disconnect the vacuum hose from the vacuum
pipe.
2. Blow through the solenoid valve from vacuum hose
A.
3. Check that air flows from port B.
76G04C-146
4C-78

4C EEC SYSTEM
EVAPORATIVE EMISSION CONTROL
(EEC)
SYSTEM
Water thermo sensor
76G04C-150
Unleaded fuel:
This system stores fuel vapor generated in the fuel tank in the canister when the engine is not running.
The fuel vapor is stored in the canister until it is drawn into the dynamic chamber and burned when
the engine is started.
Leaded fuel:
Fuel vapor generated in the fuel tank flows out to the atmosphere.
COMPONENT DESCRIPTION
Application
Component Function Remark New
model Prevtoui model
Air flow sensor Detects amount of intake air; sends signal to engine control unit
O X
Charcoal canister Stores fuel tank fumes while engine stopped
o X
Engine control unit Detects signals from input sensors and
switches; controls solenoid valves (Purge
control)
o X
Ne signal pick-up Detect crank angle at 180° intervals; sends signal to engine control unit
Installed in distributor o X
Separator Prevents fuel from flowing into charcoal canister
o o
Solenoid valve
(No.1 purge control)
Controls vacuum to solenoid valve (No.2
purge control) and vacuum switch valve
0 X
Solenoid valve (No.2 Purge control)
Controls vacuum to vacuum switch valve o X
Three-way check valve Controls pressure in fuel tank o X
Two-way check valve Controls pressure in fuel tank X o
Vacuum switch valve Regulates evaporative fumes from canis-ter to intake manifold
o X
Water thermo sensor Detects coolant temperature; sends signal to engine control unit
0 X
76G04C-151
4C-80

CONTROL SYSTEM 4C
CONTROL SYSTEM
Throttle sensor
Solenoid Solenoid Idle valve valve switch (VIC) (PRC)
Solenoid
valve
control)*
Solenoid valve
'(No.1 purge control)*1
E/L control unit
Engine control unit
Control relay
Injector
Knock sensor* -
Water thermo
switch*1
"1...Unleaded fuel
*2...Leaded fuel
Oxygen Distributor Water thermo sensor*1 sensor
Clutch switch
Oxygen sensor
relay*1
Solenoid valve
(EGR)*1
/ Solenoid valve 7 (ISC)
Air flow sensor
Neutral switch
76G04C-166
The control system consists of the input devices and the engine control unit. The control unit controls
the fuel injection amount (EGI), fuel injection pressure, bypass air amount, ignition timing, switch moni-
tor function, and fail-safe function.
4C-91

4C CONTROL SYSTEM
RELATIONSHIP CHART
Output Devices
and
Input Devices (Unleaded fuel)
IGNITION SWITCH
(ON POSION) X X X X X O X X X X X X X X O
TEST CONNECTOR X X X O X X X X X X X X X O X
ELECTRICAL LOAD CONTROL UNIT X X X o X X X X X X X X X X X
P/S PRESSURE SWITCH X X X o X X X X X X X X X X X
A/C SWITCH X X X o X X X X X X X X O X X
IGNITION SWITCH
(STA POSITION) O O X o O X X X X O X X X O X
NEUTRAL
AND

CLUTCH SWITCH O X X o X X X X X X X X X X X
OXYGEN SENSOR o X X X X X X X X X X X X X X
WATER THERMO
SWITCH (RADIATOR) o X X X X X X X o X X X X X X
INTAKE
AIR

THERMO SENSOR X X X X X X X X X O X X X X X
WATER
THERMO SENSOR o X X o X X o o O O X X X O o
IDLE SWITCH o X X o X X X X X o X X X O X
THROTTLE SENSOR o X X X X X X X O X X X X o X
AIR FLOW SENSOR o X X X X X X o X X X X X o O
Ne SIGNAL o o X O o X X O O O o o X o O
G SIGNAL X O X X X X X X X X X X X X X

\
INPUT

DEVICE
OUTPUT
DEVICE
FUEL
INJECTION
AMOUNT FUEL

INJECTION

TIMING
AIR
VALVE

ISC
VALVE
FUEL
PUMP

CONTROL
MAIN
POWER
CONTROL
SOLENOID
VALVE
(No.1
PURGE)
SOLENOID
VALVE
(No.2
PURGE)
SOLENOID
VALVE
(EGR)
SOLENOID

VALVE

(PRESSURE

REGULATOR
CONTROL)
SOLENOID
VALVE

(VARIABLE

INERTIA
CONTROL)

OXYGEN

SENSOR
RELAY
I A/C

RELAY

IGNITER
AIR

FLOW
SENSOR
(BURN-OFF)
\
INPUT

DEVICE
OUTPUT
DEVICE
INJECTOR
BAC
VALVE

CONTROL
RELAY
SOLENOID
VALVE
(No.1
PURGE)
SOLENOID
VALVE
(No.2
PURGE)
SOLENOID
VALVE
(EGR)
SOLENOID

VALVE

(PRESSURE

REGULATOR
CONTROL)
SOLENOID
VALVE

(VARIABLE

INERTIA
CONTROL)

OXYGEN

SENSOR
RELAY
I A/C

RELAY

IGNITER
AIR

FLOW
SENSOR
(BURN-OFF)

76G04C-167
4C—92