2004 DAEWOO LACETTI Service Repair Manual

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Page 305 of 2643

DAEWOO LACETTI 2004 Service Repair Manual ENGINE CONTROLS 1F – 59
DAEWOO V–121 BL4
Malfunction Indicator Lamp On Steady (1.4L/1.6L DOHC)
StepActionValue(s)YesNo
1Perform an On–Board Diagnostic (EOBD) system
check.
Is the check complet

Page 306 of 2643

DAEWOO LACETTI 2004 Service Repair Manual 1F – 60IENGINE CONTROLS
DAEWOO V–121 BL4
MALFUNCTION INDICATOR LAMP ON STEADY
(1.8L DOHC)
Circuit Description
When the ignition switch is turned ON, the Malfunction In-
dicator Lamp (MIL) will be

Page 307 of 2643

DAEWOO LACETTI 2004 Service Repair Manual ENGINE CONTROLS 1F – 61
DAEWOO V–121 BL4
Malfunction Indicator Lamp On Steady (1.8L DOHC)
StepActionValue(s)YesNo
1Perform an On–Board Diagnostic (EOBD) system
check.
Is the check complete.–

Page 308 of 2643

DAEWOO LACETTI 2004 Service Repair Manual 1F – 62IENGINE CONTROLS
DAEWOO V–121 BL4
FUEL SYSTEM DIAGNOSIS
Circuit Description
The fuel pump is an in–tank type mounted to a fuel sender
assembly. The fuel pump will remain on as long as the

1F – 62IENGINE CONTROLS
DAEWOO V–121 BL4
FUEL SYSTEM DIAGNOSIS
Circuit Description
The fuel pump is an in–tank type mounted to a fuel sender
assembly. The fuel pump will remain on as long as the en-
gine is cranking or running and the Engine Control Module
(ECM) is receiving reference pulses from the crankshaft
position (CKP) sensor. If there are no reference pulses,
the ECM will turn off the fuel pump two seconds after the
ignition switch is turned ON or two seconds after the en-
gine stops running. The fuel pump delivers fuel to the fuel
rail and the fuel injectors, where the fuel system pressure
is controlled from 284 to 325 kPa (41 to 47 psi) by the fuel
pressure regulator. The excess fuel is returned to the fuel
tank.
Test Description
The number(s) below refer to step(s) on the diagnostic
table.
2. When the engine is idling, the intake manifold vacu-
um is high. This vacuum is applied to the fuel pres-
sure regulator diaphragm, offsetting the spring
pressure inside the fuel pressure regulator and low-
ering the fuel pressure.10. If there is fuel bleeding back through the fuel return
outlet, this is due to a faulty fuel pressure regulator.
14. Another symptom often present when the fuel injec-
tors are leaking is hard starting. Leaking fuel injec-
tors can cause a flooding condition.
23. Fuel leaking from the fuel pump inlet is due to a
faulty one–way check valve in the fuel pump.
CAUTION : The fuel system is under pressure. To
avoid fuel spillage and the risk of personal injury or
fire, it is necessary to relieve the fuel system pressure
before disconnecting the fuel lines.
CAUTION : Do not pinch or restrict nylon fuel lines to
avoid damage that could cause a fuel leak, resulting
in possible fire or personal injury.
Fuel Pressure Relief Procedure
1. Remove the fuel cap.
2. Remove the fuel pump fuse EF18 from the engine
fuse box.
3. Start the engine and allow the engine to stall.
4. Crank the engine for an additional 10 seconds.
Fuel System Diagnosis
StepActionValue(s)YesNo
11. Relieve the fuel system pressure.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure within the values specified and
holding steady?284~325 kPa
(41~47psi)Go to Step 2Go to Step 4
21. Allow the engine to idle.
2. Disconnect the vacuum hose from the fuel
pressure regulator.
3. Connect a vacuum pump with a gauge to the
fuel pressure regulator vacuum port.
4. Apply 41~47 kPa (12~14 in. Hg) of vacuum to
the fuel pressure regulator.
Does the fuel pressure decrease?–Go to Step 3Go to Step 15
31. Locate and correct the cause of the vacuum
restriction to the fuel pressure regulator.
2. Confirm the operation of the fuel pressure reg-
ulator.
Is the repair complete?–System OK–
41. Relieve the fuel system pressure.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure within the values specified but
not holding steady?284~325 kPa
(41~47psi)Go to Step 5Go to Step 16
5Inspect the fuel lines for a leak.
Is the problem found?–Go to Step 6Go to Step 7

Page 309 of 2643

DAEWOO LACETTI 2004 Service Repair Manual ENGINE CONTROLS 1F – 63
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
61. Replace the fuel line(s) as needed.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure with

ENGINE CONTROLS 1F – 63
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
61. Replace the fuel line(s) as needed.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure within the values specified but
not holding steady?284~325 kPa
(41~47psi)System OK–
71. Remove the fuel pump assembly.
2. With the fuel pump under pressure, inspect the
fuel pump coupling hoses for leaking.
Is the problem found?–Go to Step 8Go to Step 9
81. Tighten or replace the fuel pump coupling
hoses as needed.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure within the values specified but
not holding steady?41–47 psi
(284–325 kPa)System OK–
9With the fuel system under pressure, inspect the fuel
return outlet for leaking.
Is the problem found?–Go to Step 10Go to Step 11
101. Replace the fuel pressure regulator.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure within the values specified but
not holding steady?284~325 kPa
(41~47psi)System OK–
11With the fuel system under pressure, inspect the fuel
inlet for leaking.
Is the problem found?–Go to Step 12Go to Step 13
121. Replace the fuel pump assembly.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure within the values specified but
not holding steady?284~325 kPa
(41~47psi)System OK–
131. Remove the fuel rail and the fuel injectors as
an assembly.
2. With the fuel system under pressure, inspect
all of the fuel injectors for leaking.
Is the problem found?–Go to Step 14–
141. Replace the leaking fuel injector(s).
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure within the values specified but
not holding steady?284~325 kPa
(41~47psi)System OK–
151. Replace the fuel pressure regulator.
2. Disconnect the fuel pressure regulator vacuum
hose.
3. Start the engine.
4. Allow the engine to idle.
5. Connect the fuel pressure regulator vacuum
hose.
Does the fuel pressure decrease?–System OK–

Page 310 of 2643

DAEWOO LACETTI 2004 Service Repair Manual 1F – 64IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
161. Relieve the fuel system pressure.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel system pressure

Page 311 of 2643

DAEWOO LACETTI 2004 Service Repair Manual ENGINE CONTROLS 1F – 65
DAEWOO V–121 BL4
FUEL PUMP RELAY CIRCUIT CHECK (1.4L/1.6L DOHC)
Circuit Description
When the ignition switch is turned ON, the Engine Control
Module (ECM) will supply batt

Page 312 of 2643

DAEWOO LACETTI 2004 Service Repair Manual 1F – 66IENGINE CONTROLS
DAEWOO V–121 BL4
Fuel Pump Relay Circuit Check (1.4L/1.6L DOHC)
StepActionValue(s)YesNo
11. Turn the ignition OFF for 10 seconds.
2. Turn the ignition ON.
3. Listen for

1F – 66IENGINE CONTROLS
DAEWOO V–121 BL4
Fuel Pump Relay Circuit Check (1.4L/1.6L DOHC)
StepActionValue(s)YesNo
11. Turn the ignition OFF for 10 seconds.
2. Turn the ignition ON.
3. Listen for in–tank fuel pump operation.
Does the fuel pump operate for the time specified?2 secSystem OKGo to Step 2
21. Turn the ignition OFF.
2. Disconnect the fuel pump relay.
3. Connect a test light between the fuel pump
relay connector terminal 30 and ground.
Turn the ignition ON. Is the test light on?–Go to Step 3Go to Step 8
31. Turn the ignition OFF.
2. Connect a test light between the fuel pump
relay connector terminal 86 and battery posi-
tive.
3. Turn the ignition ON.
4. With the ignition ON, the test light should light
for the time specified.
Is the test light on?2 secGo to Step 4Go to Step 9
41. Turn the ignition OFF.
2. Connect a test light between the fuel pump
relay connector terminal 30 and ground.
Is the test light on?–Go to Step 5Go to Step 11
5Check for an open or short to ground in the wire be-
tween the fuel pump relay connector terminal 87 and
the fuel pump connector terminal 3.
Is the problem found?–Go to Step 6Go to Step 7
61. Repair the wire between the fuel pump relay
connector terminal 87 and the fuel pump con-
nector terminal 3.
2. Install the fuel pump relay.
3. Turn the ignition OFF for 10 seconds.
4. Turn the ignition ON.
Does the fuel pump operate for the time specified?2 secSystem OK–
71. Replace the fuel pump relay.
2. Turn the ignition OFF for 10 seconds.
3. Turn the ignition ON.
Does the fuel pump operate for the time specified?2 secSystem OK–
8Check for an open wire between the fuel pump relay
connector terminal 30 and the battery.
Is the problem found?–Go to Step 13–
9Check for an open wire between the fuel pump relay
connector terminal 86 to the engine control module
(ECM) connector terminal 6.
Is the problem found.–Go to Step 10Go to Step 12
101. Repair the wire between the fuel pump relay
connector terminal 86 to the ECM connector
terminal 6.
2. Install the fuel pump relay.
3. Turn the ignition OFF for 10 seconds.
4. Turn the ignition ON.
Does the fuel pump operate for the time specified?2 secSystem OK–

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