engine MAZDA 626 1987 Workshop Manual

4B FUEL SYSTEM
TROUBLESHOOTING
Check
the
condition
of
the wiring harness and connectors before checking
the
sensors
or
switches.
Possible
cause
Page

V
S E
i
o

o V)
0
e
~
0)
Ju
»
•E
<»
CL
01
3
0
<0
1
£
Oxygen

sensor

s c V
in
V

P
o E k_

•E **
l_
h
O
v
w
Water
thermo
switch

Q.
E
3 Q.
u

Injector

£ 3 3 o d
aj
Engine
con-
trol unit terminal
< £
8
<
Q. Oxygen

sensor

£ t->
0)
>
M Water
thermo
switch
3
u.
Injector
3
u. 3C
3E
3B
Symptom 4B-94 4B-99 4B—98 4B-95 48—97 4B-97 4B-49 4B-S1 4B-48 4B-90 4B-90
Hard start
or
won't start (Cranks
OK)
5 4 1 3 2

Engine While warming
up
4 3 2 1 5

stalls After warming
up
1 3 2 4

Rough Idle While warming
up
4 3 2 1

Rough Idle After warming
up
1 2 4 3

Poor acceleration, hesitation,
or

lack
of
power
1 3 4 2

Runs rough
on
deceleration
1 2

Afterburn
in
exhaust system
1 2

Poor fuel consumption
5 6 4 3 2 1

Falls emission test
1 2

Engine stalls
or
rough after
hot
starting
1 3 2

76G04B-059
4B—44

FUEL SYSTEM 4B
86U04A-068
FUEL PRESSURE RELEASE AND SERVICING
FUEL SYSTEM
Fuel in the fuel system remains under high pressure
even when the engine is not running.
a) Before disconnecting any fuel line, release the fuel
pressure from the fuel system to reduce the pos-
sibility of injury or fire.
1. Start the engine.
2. Disconnect the circuit opening relay.
3. After the engine stalls, turn OFF the ignition
switch.
4. Reconnect the circuit opening relay.
b) Use a rag as protection from fuel spray when dis-
connecting the hoses.
Plug the hoses after removal.
c) When inspecting the fuel system, use the SST.
86U04A-069
4B—45

4B FUEL SYSTEM
76G04B-061
I i. i { 1 t' i 1 I • i i 1 1 "1 —r
1 . . • , 1 ,
EDO 250
86U04A-074
w Test connector
(Yellow)
86U04A-075
Lever
To fuel pump To pulsation damper
FUEL PRESSURE
Note
a) When inspecting fuel pressure, use the
SST. (Refer to page 4B—47).
b)Warm up the engine to normal operating
temperature.
Injection Pressure
1. Set the lever on the adapter as shown in the figure.
2. Run the engine and measure the injection pres-
sure at various speeds.
Injection pressure: Approx. 235—275 kPa
(2.4—2.8 kg/cm2, 34—40 psi)
3. If not within specification, check the fuel pump pres-
sure and fuel line pressure.
Fuel Pump Pressure
1. Connect the terminals of the test connector (Yel-
low) with a jumper wire.
2. Turn the ignition switch ON to operate the fuel
pump.
3. Set the lever on the adapter as shown in the figure.
4. Check the fuel pump pressure.
Fuel pump pressure: 441—588 kPa
(4.5—6.0 kg/cm2, 64—85 psi)
5. If the fuel pump pressure is not within specifica-
tion, check the following;
No pressure
• Fuel pump operation (Refer to page
4B—49.)
Low pressure
• Fuel pump feeding capacity (Refer to
page 4B—50.)
High pressure
• Replace the fuel pump
6. After checking the fuel pump pressure, disconnect
the jumper wire from the test connector.
76G04B-062
4B—48

FUEL SYSTEM 4B
76G04B-126
86U04A-078
V^AN.
- Test connector
(Yellow)
76G04B-063
Fuel Line Pressure
1. Start the engine and run it at idle.
2. Set the lever on the adapter as shown in the figure.
3. Check the fuel line pressure.
Fuel line pressure: Approx. 186—226 kPa
(1.9—2.3 kg/cm2, 27—33 psi)
4. If not within specification, check the vacuum hose.
5. Disconnect the vacuum hose from pressure regu-
lator, and place a finger over the end of the hose.
6. Check the fuel line pressure.
Fuel line pressure: 235—275 kPa
(2.4—2.8 kg/cm2, 34—40 psi)
7. If not within specification, replace the pressure
regulator.
8. Connect the vacuum hose to pressure regulator.
FUEL PUMP
Operation Test
1. Connect a jumper wire to the test connector
(Yellow).
2. Remove the fuel filler cap.
3. Turn the ignition switch ON.
4. Listen for operational sound of the fuel pump at
the filler inlet.
5. Install the fuel filler cap.
6. If no sound is heard, check the voltage at the fuel
pump connector (WY wire and a ground).
Voltage: 12V
7. If the voltage is normal, replace the fuel pump.
8. If not correct, check the circuit opening relay (Re-
fer to page 4B—86) and its circuits.
9. Disconnect the jumper wire.
76G04B-064
4B—49

4B FUEL SYSTEM
Volume Test
Warning
Before performing following procedures, re-
lease the fuel pressure to reduce the possi-
bility of injury or fire. (Refer to page 4B—45)
1. Connect a jumper wire to test connector (Yellow).
2. Disconnect the fuel return hose from fuel return
pipe.
76G04B-065
3. Turn the ignition switch ON for 10 seconds, and
check the feeding capacity with graduated
cylinder.
Feeding capacity:
220 cc (13.4 cu in)/10 sec. min.
4. If not within specification, check the fuel filter, and
fuel line.
5. Turn the ignition switch OFF and disconnect the
jumper wire.
86U04A-082
PULSATION DAMPER
1. Run the engine at idle.
2. Place a finger on the screw of the pulsation damper
head.
3. Check that pulsation is felt.
86U04A-083
4B—50

FUEL SYSTEM 4B
INJECTOR
On-vehicle Inspection
If engine runs
1. Warm up the engine and run it at idle.
2. Listen for operational sound of the injector with a
screwdriver or a sound scope.
3. If no operational sound is heard, check the main
relay and injector resistance.
76G04B-066
4. Disconnect the connector from each injector
respectively.
5. Check that the engine speed decreases about
100—200 rpm each time.
6. If not correct, check the injector resistance and in-
jection volume of the injector.
76G04B-067
Inspection
There are 3 inspections which must be performed for
the injectors.
Resistance
1. Remove the injectors from the engine. (Refer to
page 4B—58.)
2. Check the resistance of each injector with an
ohmmeter.
3. If not correct, replace the injector.
Resistance: 12—16 ft
76G04B-068
' Grommet Delivery pipe
76G04B-069
Fuel leakage test and volume test
1. Lift the dynamic chamber upward.
2. Remove the injectors and delivery pipe. (Refer to
pages 4B—58 and 59.)
3. Affix the injectors, pressure regulator, and pulsa-
tion damper to the delivery pipe with wire.
Caution
Affix the injectors firmly to the delivery pipe
so that no movement of the injectors is
possible.
Warning
Be extremely careful when working with fuel.
Always work away from sparks or open
flames.
4B—51

FUEL SYSTEM 4B
PRESSURE REGULATOR CONTROL SYSTEM
Water thermo sensor
*
Fuel
(To fuel tank)
76G04B-072
To prevent percolation of the fuel during idle after the engine is restarted, vacuum is cut to the pres-
sure regulator, increasing the fuel pressure.
Specified time: Approx. 120 sec.
Operating condition: Coolant temperature — above 70°C (158°F)
Intake air temperature — above 10°C (50°F)
4B—53

4B FUEL SYSTEM
COMPONENT DESCRIPTIONS
Component Function Remarks
Engine control unit Detects signals from input sensors and
switches; controls solenoid valve (Pres-
sure regulator control)
Idle switch Detects when throttle valve fully closed; sends signal to engine control unit Installed in throttle sensor
Ignition coil (-) terminal Detects engine speed; sends signal to engine control unit
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
Installed in air flow meter
Pressure regulator Adjusts fuel pressure supplied to injectors
Solenoid valve (Pres-sure regulator control) Controls vacuum line to pressure regulator Closes vacuum line when hot
Water thermo sensor Detects coolant temperature; sends signal to engine control unit
76G04B-073
4B—54

FUEL SYSTEM 4B
TROUBLESHOOTING
Check the condition of the wiring harness and connections before checking the sensors or switches
below.
Note
Make the system inspection first. If no problem is found, continue with the next system
inspection of the Troubleshooting Guide. (Refer to pages 4B—7 and 8.)
Possible \ cause
\ Page
Solenoid valve (Pres-sure regula-tor control)
Water thermo
sensor Intake air
thermo sensor
Engine con-trol unit terminal
2K
System inspection
Symptom 4B—56 4B—97 4B—94 4B—89 4B—55
Engine stalls or rough after hot starting 2 3
A
5 1
76G04B-074
System Inspection
1. Connect the SST to the engine. (Refer to page
4B—47.)
2. Start the engine.
76G04B-075
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. Lift the air cleaner upper cover assembly.
5. Heat the intake air thermo sensor to above 10°C
(50 °F).
76G04B-076
4B—55

4B FUEL SYSTEM
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)
6. Restart the engine.
7. Check the fuel line pressure and operating times
as shown in the chart.
76G04B-127
Solenoid Valve (Pressure Regulator Control)
Inspection
1. Disconnect the vacuum hose from the solenoid
valve and vacuum pipe.
2. Blow through the solenoid valve from vacuum hose
A.
3. Check that air flows from port B.
86U04A-098
Air filter
Apply 12V
Port (J)
4. Disconnect the solenoid valve connector.
5. Connect 12V and a ground to the terminals of the
solenoid valve.
6. Blow through the solenoid valve from the vacuum
hose A.
7. Check that air flows from the valve air filter.
86U04A-099
4B-56