Daewoo Nubira. Manual — part 117

1F – 50

I

ENGINE CONTROLS

DAEWOO V–121 BL4

Step

No

Yes

Value(s)

Action

5

1. 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

(41–47 psi)

Go to Step 6

Go to Step 17

6

Inspect the fuel lines for a leak.
Is the problem found?

Go to Step 7

Go to Step 8

7

1. 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

(41–47 psi)

System OK

8

1. 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 9

Go to Step 10

9

1. 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?

284–325 kPa

(41–47 psi)

System OK

10

With the fuel system under pressure, inspect the fuel
return outlet for leaking.
Is the problem found?

Go to Step 11

Go to Step 12

11

1. 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

(41–47 psi)

System OK

12

With the fuel system under pressure, inspect the fuel
inlet for leaking.
Is the problem found?

Go to Step 13

Go to Step 14

13

1. 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

(41–47 psi)

System OK

14

1. 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 15

15

1. 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

(41–47 psi)

System OK

ENGINE CONTROLS 1F – 51

DAEWOO V–121 BL4

Step

No

Yes

Value(s)

Action

16

1. 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

17

1. 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

(41–47 psi)

Go to Step 13

Go to Step 18

18

1. 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

(41–47 psi)

Go to Step 19

19

Inspect the fuel lines for leaks.
Is the problem found?

Go to Step 7

Go to Step 20

20

1. 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 9

Go to Step 21

21

1. 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 11

Go to Step 22

22

1. 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 13

Go to Step 23

23

1. 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 15

Go to Step 13

1F – 52

I

ENGINE CONTROLS

DAEWOO V–121 BL4

FUEL PUMP RELAY CIRCUIT CHECK

Circuit Description

When the ignition switch is turned ON, the powertrain con-
trol module (PCM)/engine control module (ECM) will acti-
vate the fuel pump relay and run the in–tank fuel pump.
The fuel pump will operate as long as the engine is crank-
ing or running and the PCM/ECM is receiving ignition ref-
erence pulses.

If there are no reference pulses, the PCM/ECM will shut
off the fuel pump within 2 seconds after the ignition switch
is turned ON.

Diagnostic Aids

An intermittent problem may be caused by a poor connec-

tion, rubbed through wire insulation, or a broken wire in-
side the insulation.

Test Description

The number(s) below refer to step(s) on the diagnostic
table.

3.

This step checks for the PCM/ECM providing a
ground for the operation of the fuel pump relay.

7.

By confirming that the wiring is OK using Steps 2
through 6, it can be determined that the fuel pump
relay is at fault.

9.

After determining that there is no ground being pro-
vided by the PCM/ECM to the fuel pump relay, the
fault is either the PCM/ECM or the wiring between
the PCM/ECM and the fuel pump relay.

ENGINE CONTROLS 1F – 53

DAEWOO V–121 BL4

Fuel Pump Relay Circuit Check

Step

Action

Value(s)

Yes

No

1

1. 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 sec

System OK

Go to Step 2

2

1. Turn the ignition OFF.
2. Disconnect the fuel pump relay.
3. Connect a test light between the fuel pump

relay connector terminal 86 and battery posi-
tive.

4. Turn the ignition ON.

Is the test light on?

Go to Step 3

Go to Step 8

3

1. Turn the ignition OFF.
2. Connect a test light between the fuel pump

relay connector terminal 85 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 sec

Go to Step 4

Go to Step 9

4

1. 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 5

Go to Step 11

5

Check for an open or short to ground in the wire be-
tween the fuel pump relay connector terminal 87 and
the fuel cutoff switch terminal 1.
Is the problem found?

Go to Step 6

Go to Step 7

6

1. Repair the wire between the fuel pump relay

connector terminal 87 and the fuel cutoff switch
terminal 1.

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 sec

System OK

7

1. 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 sec

System OK

8

Check for an open wire between the fuel pump relay
connector terminal 86 and the ignition 1 relay con-
nector terminal 86.
Is the problem found?

Go to Step 13

Go to ”Ignition

1 Relay Circuit

Check”

9

Check for an open wire between the fuel pump relay
connector terminal 85 to the powertrain control mod-
ule (PCM)/engine control module (ECM) connector
terminal E13.
Is the problem found?

Go to Step 10

Go to Step 12