fuel pressure DAEWOO NUBIRA 2004 Service Owner's Guide

1F – 38IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
10Replace the EGR valve.
Is the replacement complete?–Go to Step 19–
11Locate and repair the short to voltage in the MAP
sensor signal circuit.
Is the repair complete?–Go to Step 19–
12Locate and repair the short to voltage in the TP sen-
sor signal circuit.
Is the repair complete?–Go to Step 19–
13Locate and repair the short to voltage in the IAT sen-
sor signal circuit.
Is the repair complete?–Go to Step 19–
14Locate and repair the short to voltage in the ECT
sensor signal circuit.
Is the repair complete?–Go to Step 19–
15Locate and repair the short to voltage in the EGR
Pintle Position sensor circuit.
Is the repair complete?–Go to Step 19–
16Measure the voltage of the fuel tank pressure sensor
signal circuit between the ECM harness connector
and ground.
Does the voltage near the specified value?0 VGo to Step 18Go to Step 17
17Locate and repair the short to voltage in the fuel tank
pressure sensor signal circuit.
Is the replacement complete?–Go to Step 19–
18Replace the ECM.
Is the repair complete?–Go to Step 19
191. Using the scan tool, clear the Diagnostic
Trouble Codes (DTCs).
2. Start the engine and idle at normal operating
temperature.
3. Operate the vehicle within the conditions for
setting the DTCs as specified in the supporting
text.
Does the scan tool indicate that this diagnostic ran
and passed?–Go to Step 20Go to Step 2
22Check if any additional DTCs are set.
Are any DTCs displayed that have not been diag-
nosed?–Go to applica-
ble DTC tableSystem OK

1F – 42IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
191. Measure the resistance between following ter-
minals:
S Terminal 1 and 2 of ignition coil.
S Terminal 2 and 1 of ignition coil.
Are the resistance within the value specified.
1. Remove the high tension cable.
2. Measure the resistance between second coil.
S Between 1 and 4
S Between 2 and 3
Are the resistance within the value specified.0.9 W
5.3 kWGo to Step 21Go to Step 20
20Replace the EI system ignition coil.
Is the repair complete?–Go to Step 2–
211. Check for any damages or poor connection in
ignition wires and repair as needed.
2. Connect the EI system ignition coil connector
and ECM connector.
3. Check for the presence of spark from all of the
ignition wires.
Is the spark present from all of the ignition wires?–Go to Step 2Go to Step 22
22Replace ECM.
Is the repair complete?–Go to Step 2–
231. Turn the ignition OFF.
2. Connect a fuel pressure gauge.
3. Crank the engine.
Is any fuel pressure present?–Go to Step 26Go to Step 24
241. Turn the ignition OFF.
2. Disconnect the electrical connector at the fuel
pump.
3. Connect a test light between the fuel pump ter-
minals 2 and 3.
4. Turn the ignition ON.
5. With the ignition ON, the test light should light
for the time specified.
Is the test light on?2 sec.Go to Step 25Go to 34
25Replace the fuel pump.
Is the repair complete?–Go to Step 2–
26Is the fuel pressure within the value specified?283–324 kPa
(41–47 psi)Go to Step 27Go to Step 29
27Check the fuel for contamination.
Is the fuel contaminated?–Go to Step 28Go to Step 41
281. Remove the contaminated fuel from the fuel
tank.
2. Clean the fuel tank as needed.
Is the repair complete?–Go to Step 2–
291. Check the fuel filter for restriction.
2. Inspect the fuel lines for kinks and restrictions.
3. Repair or replace as needed.
4. Measure the fuel pressure.
Is the fuel pressure within the value specified?283–324 kPa
(41–47 psi)Go to Step 2Go to Step 30

ENGINE CONTROLS 1F – 43
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
301. Disconnect vacuum line from the fuel pressure
regulator.
2. Inspect the vacuum line for the presence of
fuel.
3. Inspect the fuel pressure regulator vacuum port
for the presence of fuel.
Is any fuel present?–Go to Step 31Go to Step 32
31Replace the fuel pressure regulator.
Is the repair complete?–Go to Step 2–
321. Remove the fuel pump assembly from the fuel
tank.
2. Inspect the fuel pump sender and the fuel cou-
pling hoses for a restriction.
3. Inspect the in–tank fuel filter for restriction.
Is the problem found?–Go to Step 33Go to Step 25
33Replace the fuel pump sender, the in–tank fuel filter,
and/or the fuel coupling hoses as needed.
Is the repair complete?–Go to Step 2–
341. Turn the ignition OFF.
2. Disconnect the electric connector at the fuel
pump.
3. Connect a test light between fuel pump con-
nector terminal 3 and ground.
4. Turn the ignition ON.
5. With the ignition ON, the test light should illumi-
nate for the time specified.
Is the test light on?2 secGo to Step 35Go to Step 36
35Repair the open circuit between the fuel pump con-
nector terminal 2 and ground.
Is the repair complete?–Go to Step 2–
361. Turn the ignition OFF.
2. Disconnect the fuel pump relay.
3. Turn the ignition ON.
4. Measure the voltage at terminal 30 and 86 of
fuel pump relay.
Is the voltage within the value specified?11–14 VGo to Step 38Go to Step 37
37Repair open or short circuit for power supply.
Is the repair complete?–Go to Step 2–
381. Turn the ignition OFF.
2. Disconnect ECM connector.
3. Using an ohmmeter, measure the resistance
between following terminals.
S Terminal 6 of ECM and terminal 85 of fuel
pump relay.
S Terminal 87 of fuel pump relay and terminal
3 of fuel pump.
Does the resistance within the value specified?0 WGo to Step 40Go to Step 39

1F – 50IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
35While cranking the engine, measure the voltage at
the EI system ignition coil connector terminal 3 .
Does the voltage fluctuate within the values speci-
fied?0.2–2.0 vGo to Step 39Go to Step 37
36Check for an open in the wire from the EI system
ignition coil connector terminal 1 to the ECM connec-
tor terminal M51.
Is the problem found?–Go to Step 38Go to Step 40
37Check for an open in the wire from the EI system
ignition coil connector terminal 3 to the ECM connec-
tor terminal M1.
Is the problem found?–Go to Step 38Go to Step 40
381. Repair the wiring as needed.
2. Connect the EI system ignition coil connector.
3. Check for the presence of spark from all of the
ignition wires.
Is spark present from all of the ignition wires?–Go to Step 3Go to Step 39
39Replace the EI system ignition coil.
Is the repair complete?–Go to Step 3–
401. Turn the ignition OFF.
2. Replace the ECM.
Is the repair complete?–Go to Step 3–
411. Turn the ignition OFF.
2. Connect a fuel pressure gauge.
3. Crank the engine.
Is any fuel pressure present?–Go to Step 44Go to Step 42
421. Turn the ignition OFF.
2. Disconnect the electrical connector at the fuel
pump.
3. Connect a test light between the fuel pump
connector terminals 3 and 2.
4. Turn the ignition ON.
5. With the ignition ON, the test light should light
for the time specified.
Is the test light on?2 secGo to Step 43Go to Step 53
43Replace the fuel pump.
Is the repair complete?–Go to Step 3–
44Is the fuel pressure within the value specified?283–324 kPa
(41–47 psi)Go to Step 48Go to Step 45
451. Check the fuel filter for a restriction.
2. Inspect the fuel lines for kinks and restrictions.
Is the problem found?–Go to Step 46Go to Step 47
461. Disconnect the vacuum line from the fuel pres-
sure regulator.
2. Inspect the vacuum line for the presence of
fuel.
3. Inspect the fuel pressure regulator vacuum port
for the presence of fuel.
Is any fuel present?283–324 kPa
(41–47 psi)Go to Step 3Go to Step 47

ENGINE CONTROLS 1F – 51
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
471. Disconnect the vacuum line from the fuel pres-
sure regulator.
2. Inspect the vacuum line for the presence of
fuel.
3. Inspect the fuel pressure regulator vacuum port
for the presence of fuel.
Is any fuel presen–Go to Step 50Go to Step 51
48Check the fuel for contamination.
Is the fuel contaminated?–Go to Step 49Go to Step 65
491. Remove the contaminated fuel from the fuel
tank.
2. Clean the fuel tank as needed.
Is the repair complete?–Go to Step 3–
50Replace the fuel pressure regulator.
Is the repair complete?–Go to Step 3–
511. Remove the fuel pump assembly from the fuel
tank.
2. Inspect the fuel pump sender and the fuel cou-
pling hoses for a restriction.
3. Inspect the in–tank fuel filter for a restriction.
Is the problem found?–Go to Step 52Go to Step 43
52Replace the fuel pump sender, the in–tank fuel filter,
and/or the fuel coupling hoses as needed.
Is the repair complete?–Go to Step 3–
531. Turn the ignition OFF.
2. Disconnect the electrical connector at the fuel
pump.
3. Connect a test light between the fuel pump
connector terminal 3 and a known good
ground.
4. Turn the ignition ON.
5. With the ignition ON, the test light should light
for the time specified.
Is the test light on?2 secGo to Step 54Go to Step 55
54Repair the open wire between the fuel pump connec-
tor terminal 2 and ground.
Is the repair complete–Go to Step 3–
551. Turn the ignition OFF.
2. Disconnect the fuel pump relay.
3. Connect a test light between the fuel pump
relay connector terminal 85 and ground.
4. Turn the ignition ON.
Is the test light on?2 secGo to Step 56Go to Step 62
561. 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?–Go to Step 57Go to Step 61

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

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–

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 below the values speci-
fied and holding steady?284~325 kPa
(41~47psi)Go to Step 12Go to Step 17
171. Relieve the fuel system pressure.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel system pressure below the values speci-
fied and holding steady?284~325 kPa
(41~47psi)Go to Step 17–
18Inspect the fuel lines for leaks.
Is the problem found?–Go to Step 6Go to Step 19
191. 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 20
201. Remove the fuel pump assembly.
2. With the fuel system under pressure, inspect
the fuel return outlet for leaking.
Is the problem found?–Go to Step 10Go to Step 21
211. Remove the fuel pump assembly.
2. With the fuel system under pressure, inspect
the fuel inlet for leaking.
Is the problem found?–Go to Step 12Go to Step 22
221. 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 14Go to Step 12

ENGINE CONTROLS 1F – 75
DAEWOO V–121 BL4
MANIFOLD ABSOLUTE PRESSURE CHECK
(1.4L/1.6L DOHC)
Circuit Description
The Manifold Absolute Pressure (MAP) sensor measures
the changes in the intake manifold pressure which result
from engine load (intake manifold vacuum) and rpm
changes. The MAP sensor converts these changes into a
voltage output. The engine control module (ECM) sends
a 5–volt reference voltage to the MAP sensor. As the in-
take manifold pressure changes, the output voltage of the
MAP sensor also changes. A low voltage (high vacuum)
output of 1 to 2 volts is present at idle. A high voltage (low
vacuum) output of 4.0 to 4.8 volts is present at wide open
throttle. The MAP sensor is also used under certain condi-
tions to measure baro–metric pressure. This allows the
ECM to make adjustments for altitude changes. The ECMuses the MAP sensor for fuel delivery and ignition timing
changes.
Test Description
The number(s) below refer to step(s) on the diagnostic
table.
2. Applying 34 kPa (10 inches Hg) of vacuum to the
MAP sensor should cause the voltage to change.
Subtract the second voltage reading from the first.
That voltage value should be more than 1.5 volts.
When applying vacuum to the MAP sensor, the
change in the voltage should happen instantly. A
slow voltage change indicates a faulty MAP sensor.
3. Disconnect the MAP sensor from the bracket and
twist the MAP sensor. Output changes more than
0.1 volt indicate a faulty connector or connection.

ENGINE CONTROLS 1F – 77
DAEWOO V–121 BL4
MANIFOLD ABSOLUTE PRESSURE CHECK (1.8L DOHC)
Circuit Description
The Manifold Absolute Pressure (MAP) sensor measures
the changes in the intake manifold pressure which result
from engine load (intake manifold vacuum) and rpm
changes. The MAP sensor converts these changes into a
voltage output. The engine control module (ECM) sends
a 5–volt reference voltage to the MAP sensor. As the in-
take manifold pressure changes, the output voltage of the
MAP sensor also changes. A low voltage (high vacuum)
output of 1 to 2 volts is present at idle. A high voltage (low
vacuum) output of 4.0 to 4.8 volts is present at wide open
throttle. The MAP sensor is also used under certain condi-
tions to measure baro–metric pressure. This allows the
ECM to make adjustments for altitude changes. The ECMuses the MAP sensor for fuel delivery and ignition timing
changes.
Test Description
The number(s) below refer to step(s) on the diagnostic
table.
2. Applying 34 kPa (10 inches Hg) of vacuum to the
MAP sensor should cause the voltage to change.
Subtract the second voltage reading from the first.
That voltage value should be more than 1.5 volts.
When applying vacuum to the MAP sensor, the
change in the voltage should happen instantly. A
slow voltage change indicates a faulty MAP sensor.
3. Disconnect the MAP sensor from the bracket and
twist the MAP sensor. Output changes more than
0.1 volt indicate a faulty connector or connection.