1987 MAZDA 626 Workshop Manual

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

EEC SYSTEM
4C

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
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(No.
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Solenoid

valve
(No.
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Two-way

check
valve

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Solenoid
valve
(No.
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Solenoid

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(No.
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Two-way

check
valve

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Page 4C—83 4C-84 4C-84 4C—84 4C-83 4C-85 4C-82 4C-83 4C-106 4C-107 4C—98 4C-81
Checking order (Unleaded fuel) 4 2 3 — 10 11 5 6 7 8 9 1
Checking order
(Leaded fuel) — — — 1 — 2
76G04C-152
System Inspection
1. Check
the
vacuum hose routing.
2. If there
is a
poor connection, clog,
or
leak, repair
or replace
as
necessary.
3. Warm
up the
engine
and run it at
idle.
4. Disconnect vacuum hose
A
from
No. 1
purge con-
trol valve
and
connect
the SST to the
hose.
86U04A-140
5. Increase
the
engine speed
to
above 2,500
rpm

and verify that
the
gauge shows more than
150

mmHg
(5.9
inHg).
6. If not correct, check the solenoid valve (No.
1
purge
control).
7. Reconnect hose
A to No. 1
purge control valve.
4C-81
76G04C-153

4C EEC SYSTEM
76G04C-154
76G04C-155
76G04C-156
8. Disconnect vacuum hose B from the canister and
place a finger over the end of the hose.
9. Accelerate the engine rapidly and check that vacu-
um is felt at above 1,700 rpm.
10. Reconnect hose B to the canister.
11. If not correct, check the vacuum switch valve and
the solenoid valve (No. 2 purge control).
12. Disconnect vacuum hose C from the canister and
place a finger over the end of the hose.
13. Check that vacuum is felt.
14. If not correct, check the vacuum line between the
canister and the dynamic chamber for clogging.
15. Disconnect the evaporation hose from the evapo-
ration pipe.
16. Connect a vacuum pump to the evaporation pipe.
17. Operate the vacuum pump and verify that no vacu-
um is held.
18. If vacuum is held, check the evaporation pipe for
clogging.
No. 1 Purge Control Valve
1. Blow through the purge control valve from port A
and check that air does not flow.
2. Connect a vacuum pump to the purge control
valve.
3. Apply 110 mmHg (4.33 inHg) vacuum, and blow
through port A again; air should flow.
86U04A-144
4C—82

EEC SYSTEM 4C
76G04C-157
76G04C-158
Three-way
check valve
86U04A-148
BO
To canister
Pressure valve
O A To tank
Vacuum valve
Air filter
86U04A-149
No. 2 Purge Control Valve
1. Disconnect vacuum hose D from the evaporation
pipe.
2. Blow through the hose and verify that air flows
freely.
Vacuum Switch Valve
1. Remove the vacuum switch valve.
2. Connect a vacuum pump to the valve.
3. Blow through the valve from port A and verify that
air comes out of port B when vacuum is applied.
Specified vacuum:
66—106 mmHg (2.6—4.2 inHg)
Three-Way Check Valve
1. Remove the check valve.
2. Blow through the valve from port A, and check that
air comes out of port B.
Next, block port B and check that air comes out
of port C.
3. Block port B.
4. Connect a vacuum pump to port A and verify that
no vacuum is held.
4C—83

4C EEC SYSTEM
Solenoid Valve
1. Remove the solenoid valve.
76G04C-159
2. Connect vacuum hoses to the valve as shown in
the figure.
3. Blow air through the valve from hose A and check
that air comes out of the valve air filter.
4. Apply 12V and ground the solenoid valve with jum-
per wires.
5. Blow air through the valve from hose A and check
that the air comes out of port B.
6. Replace, if necessary.
86U04A-151
Two-way check valve
Inspection
1. Remove the two-way check valve.
76G04C-160
4C-84
Connect a pressure gauge to the passage that nor-
mally is connected to the fuel tank.
Blow through the valve from port A. Verify that the
valve opens at 2.94 kPa (0.03 kg/cm2,0.43 psi).
Remove the pressure gauge and connect
it
to the
passage to atmosphere.
Blow through the valve from port B. Verify that the
valve opens at 0.98 kPa (0.01 kg/cm2,0.14 psi).

EEC SYSTEM 4C
®(
Atomosphere
side Fuel tank side
76G04C-212
Replacement
1. Remove the two-way check valve.
2. Install a new valve so that the arrow on the valve
faces atmosphere side.
— - ...
h§§
IB// i \
1 S LCD \
1

J M
J k
Separator
^ X
IB// i \
1 S LCD \
1

J M
J k ==J/
J——K
1
Separator
1. Remove the separator.
2. Visually check the separator for damage.
3. Replace, if necessary.
86U04A-154
4C—85

4C PCV SYSTEM
POSITIVE CRANKCASE VENTILATION
(PCV)
SYSTEM
PCV valve
76G04C-162
The PCV valve is operated by the intake manifold vacuum.
When the engine is running at idle, the PCV valve is opened slightly and a small amount of blow-by
gas is drawn into the dynamic chamber.
At high engine speeds, the PCV valve is further opened and a larger amount of blow-by gas is drawn
into the dynamic chamber.
COMPONENT DESCRIPTION
Component Function Remark
PCV valve Controls blowby gas amount pulled into engine
PCV VALVE
1. Warm up the engine to the normal operating tem-
perature and run it at idle.
2. Disconnect the PCV valve and the ventilation hose
from the cylinder head cover.
3. Close the PCV valve opening.
4. Check that vacuum is felt.
86U04A-157
4C-86

EXHAUST SYSTEM (UNLEADED FUEL) 4C
EXHAUST SYSTEM (UNLEADED FUEL)
Exhaust manifold
Catalytic converter
Main silencer
Middle pipe
76G04C-163
The catalytic converter is used to reduce CO and HC. The converter contains a compound of plati-
num and rhodium. It is a two-way catalyst type with a volume of 2,300 cc (140 cu in).
4C—87