1987 MAZDA 626 coolant

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

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 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

4C CONTROL SYSTEM
Output Devices
and
Engine Conditions (Unleaded fuel)

REMARK

*
Above

7,000

rpm:

fuel

cut

'Coolant

temp.:
below

50°C

(122°F)

41 Coolant
temp:

below

70°C

(158°F)

*2 Engine
speed
above
1,700
rpm
*3 Engine

speed:

1,500—3,500

rpm

*
During
hot

start

only

*
Engine
speed:
above

5,200

rpm

'Engine

speed:
above

3,000

rpm

'Delays

0.5
second

IGN:

ON

(ENGINE
NOT RUNNING)

No

injection

No bypass OFF
(main

fuel

pump

not
operated)
OFF
OFF
z
1

IDLE

(THROTTLE
VALVE
FULLY CLOSED)
Rich

and

i
lean
Sequential
(once

per

two

revolutions)
OFF

o en C3 UJ
z
"After

start-
ing:

ON

(Vacuum

cut) OFF
o

DECELE-
RATION
'Fuel

cut

L

Small
amount
of
bypass
air
N (1st
stage
operate:

o
o Ho 3 O CO CD > CO >
>; CO
CO c o
c o o

HEAVY
LOAD
•ST c
Closed

Small
amount
of
bypass
air

-co-CD CO
N (1st
stage
operate:

In CD 2? 03 a. o CD o> CO to "O c

*3 OFF (EGR)

o Ho 3 O CO CD > CO >
03 k-o CO c 03 CO z o *
CD c O) c 03 c o
c o o a 3

ACCELE-
RATION
Rich

o •*—• 3 o > CD
O

Small
amount
of
bypass
air

03 Q. O Q. E 3

ON

O
In CD 2? 03 a. o CD o> CO to "O c
ON
(EGR cut)
:F (Vacuum
to
pressure

regulatt

03 3 -C CO o
c 03 CS3 > X o o
z o * CO •o c CD Q. CD T3
C CO CD o "O 3= O c: 3 CO
LL LL o

MEDIUM
LOAD
WARM
Rich

and lean

|
Q. CD O
CD D
C CO E
CVJ.
z o fS *
*3 OFF (EGR)
:F (Vacuum
to
pressure

regulatt

E 3 3
c 03 i t 3 G, LL LL
T3 CD O c CO > "O <
C CO CD o "O 3= O c: 3 CO
LL LL o

MEDIUM
LOAD

COLD

ro
c CD 3 cr
z O "a CD a? CD CL o

F (2nd
stage
not
operated)
:F (Vacuum
to
pressure

regulatt

z o * O «

WARMING
UP

(DURING
IDLE)
Rich

CD CO c CD Q-O
o
c 3 CO O CO E CO
o c F (2nd
stage
not
operated)

tr O UJ
z o
O
LL z
Fixed

at

BTDC

12°

CRANKING
(COLD
ENGINE)
1
group
(twice

per

revolution)

CO
«
CD urn i CO
CO
LL LL O
LL O * « o o
LL LL o
Fixed
at

BTDC

6°

z o

SOLENOID
VALVE
(PRESSURE
REGU-

LATOR

CONTROL)

CC
o z o o iii z
o z 111

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
REGU-

LATOR

CONTROL)
SOLENOID
VALVE
(VARIABLE
INE
TIA
CONTROL)

> <
Ul oc oc o
£T u. O 1 z oc 3 m
oc o

OUTPUT
DEVICE
INJECTOR
BAC
VALVE
CONTROL
RELAY
SOLENOID
VALVE
(No.1
PURGE)
SOLENOID

VALVE

(NO.2

PURGE)
SOLENOID
VALVE
(EGR)
SOLENOID
VALVE
(PRESSURE
REGU-

LATOR

CONTROL)
SOLENOID
VALVE
(VARIABLE
INE
TIA
CONTROL)

tn z Ul (0 z Ul o >-X o
A/C

RELAY

IGNITER

z Ul (O
=5 o
IL oc <
76G04C-169
4C—94

CONTROL SYSTEM
4C

Output Devices
and
Engine Conditions (Leaded fuel)

REMARK

E Q
O O O r-»" CD > o n <

fuel
cut

'Coolant

temp.:

below

50°

(122°F)

*
During

hot
starting
only

*
Engine

speed:

above

5,400

rpm

'Delays

0.5

seconds

IGN:
ON
(ENGINE
I
NOT
RUNNING)

o
z
injection
No
bypass
OFF

(main

fuel

pump

not
operated)
OFF
LL
I

IDLE
(THROTTLE
VALVE
FULLY
CLOSED)
Rich

I
Sequential (once
per
two

revolutions)
"After

start-
ing:
ON

(vacuum

cut)
O

DECELE-
RATION

i

i
'Fuel

cut

•o CD CO "co" CD ts o to 3 o CO CD > CO
CO c o
c o o

HEAVY
LOAD
sz "co" c
O o CO CO CO Q. >. -O
O
CD Q. O CL E CL ® D
C CO F
o 08 3 u> £ CD 3 CO 0) CD
o to 3 o CO CD > CO
z

c o o c
B

ACCELE-RATION

ir o 3 0 > CD 1 O
C
O E CO
"CO
CD Q. O CL E CL ® D
C CO F
z

o 08 3 u> £ CD 3 CO 0) CD
CD e 3 SZ CO o
O * CO
c CD CL CD T3
c CO 8 "D

'
MEDIUM
LOAD
WARM
Normal

CD Q. CD O
E CO
z
O
o o_ O
E
3 3
o CO ^ LL LL O
E 3 3 O CO
•o "O <
c
3
m
LL LL o

'
MEDIUM
LOAD
COLD

.H C CD 3 CT
o_ O
E
3 3
o CO ^ LL LL O

z
o *

WARMING
UP

(DURING
IDLE)
Rich

CD CO

*Open

B
3
CO
O
CO
E
<®
LL
Fixed

at
BTDC
12°

CRANKING
(COLD
ENGINE)
1
group
(twice

per

revolution)

CO
«
0)
>,
u>n w-CO
o

OFF
Fixed

at

BTDC

6°
ENGINE
CONDITION
OUTPUT
DEVICE
FUEL
INJECTION

AMOUNT
'
FUEL
INJECTION

TIMING
AIR

VALVE
ISC
VALVE
FUEL
PUMP
CONTROL MAIN
POWER
CONTROL
SOLENOID
VALVE
(PRESSURE
REGU-

LATOR

CONTROL)
SOLENOID
VALVE
(VARIABLE
INER-
TIA
CONTROL)

(T ik 0 1 z DC 3
ffl

OC o tn

OUTPUT
DEVICE
INJECTOR
BAC
VALVE
CONTROL
RELAY
SOLENOID
VALVE
(PRESSURE
REGU-

LATOR

CONTROL)
SOLENOID
VALVE
(VARIABLE
INER-
TIA
CONTROL)

A/C

RELAY

IGNITER

Z Ul tn
£ o
ik DC <
76G04C-170
4C—95

4C CONTROL SYSTEM
Terminal Input Output Connection to Voltage (After warming-up) Remark Terminal Input Output Connection to Ign: ON Idle Remark
10 o Air flow sensor
(Burn-off control) Below 2.5V White burning off:
Approx. 8—12V
1P o
Control relay (Power supply circuit) Below 2.5V Ignition switch OFF:
Approx. 12V
1Q 0 Control relay (Fuel pump circuit) Approx. 12V Below 2.5V
1R
(L/F) O Knock sensor OV or 2—7V While knocking:
Approx. 0.001
1S — — — — —
1T o Ignition switch
(ON position) Approx. 12V
1U — — — — —
1V — — — — —
1W o Test connector Test connector grounded: OV Test connector not grounded: approx. 12V Green connector, 1-pin
1X o Igniter Approx. 12V *Approx.1V 'Engine Signal
Monitor: green and
red lights flash
2A (U/F) o V ref 4.5—5.5V
2B o Air flow sensor
(Ground) OV
2C — — Ground (E2) OV
2D (U/F) o Oxygen sensor OV 0-1.0V
• Cold engine: 0V at idle
• After warming-up: Increase engine speed: 0.7—1.0V Deceleration: 0—0.2V
2E o Air flow sensor
(Intake air mass) 1.0—1.6V 1.7—2.3V Increase engine speed: voltage increases
2F — — — .— —
2G (U/F) o Throttle sensor Accelerator pedal released: approx. 0.5V
Max. voltage (Throt-tle valve fully opened): approx. ,4.3V
2H (L/F) o Air flow sensor (Variable resister) 0-5V Depends on
adjustment
21 o Water thermo sensor Approx. 0.4V
Engine coolant
temp. 20°C (68°F):
approx. 2.5
2J o Intake air thermo sensor (Dynamic chamber)
Approx. 2.5V at 20°C (68°F)
2K o
Solenoid valve (Pressure regula-tor control)
For 120 sec. after ignition switch OFF - ON: below 2.5V
For 120. sec after starting: below 2.5V
During hot condi-tion: Coolant temp, above 70°C (158°F) Intake air temp, above 30°C (86°F) ...Unleaded fuel above 50°C (122°F) ...Leaded fuel
2K o
Solenoid valve (Pressure regula-tor control)
ADDrox. 12V Other conditions
2L — — — — —
Note
a) Terminal labeled "U/F" are only for unleaded fuel.
b)Terminal labeled "L/F" are only for leaded fuel.
4C-100

CONTROL SYSTEM 4C
Terminal Input Output Connection to Voltage (After warming-up) Remark Terminal Input Output Connection to Ign: ON Idle Remark
2M
(U/F) o Oxygen sensor
heater Below 2.5V Above 3000 rpm: Approx. 12V
2N
(U/F) o Solenoid valve (EGR) Below 2.5V
• Radiator temp, below 17°C (62.6°F) or cool-ant temp, below 70°C (158°F): constant below 2.5 V
• 1,500-3,500 rpm: approx. 12V
20 (U/F) 0 Solenoid valve (No.2 purge control) Approx. 12V
• Coolant temp, below 75 °C (167°F): constant approx. 12V
• During medium and high load of above 1,700 rpm: below 2.5V
2P
(U/F) o
Solenoid valve
(No.1 purge
control)
Below 2.5V
Coolant temp, below 70°C (158°F): ap-prox. 12V
2Q o Solenoid valve (Idle speed control) Approx. 9—11V
2R — — Ground (E02) OV
3A — — Ground (E01) OV
3B O Ignition switch
(Start position) Below 2.5V While cranking: ap-
Drox. 10V
3C o Injector (No.2) Approx. 12V *1 Approx. 12V
*1 Engine Signal Monitor green and red liahts flash
3D — — — — —
3E o Injector (No.1) Approx. 12V *1 Approx. 12V
*1 Engine Signal
Monitor: gree and
red liahts flash
3F 0 Injector (No.4) Approx. 12V *1 Approx. 12V
*1 Engine Signal Monitor: gree and red liahts flash
3G — Ground (E1) OV
3H o Injector (No.3) Approx. 12V 'Approx. 12V *1 Engine Signal
Monitor: green and
red lights flash
31 0 — Control relav ADDrox. 12V
3J — — Battery Approx. 12V For back-uD
76G04C-179
Note
Terminals labeled "U/F" are only for unleaded fuel.
Terminal Location
31 3G 3E 3C 3A
3J 3H 3F 3D 3B
2Q 2d 2M *
L CM
2G 2E 2C <
CM

2R 2P 2N 2L 2J 2H 2F 20 2B
1W 1U 1S 1Q 10 1M 1K 11 1G 1E 1C 1A
1X 1V 1T 1R 1P 1N 1L 1J 1H 1F 1D 1B
4C-101