Daewoo Matiz (2003 year). Manual - part 31

1F – 34 ENGINE CONTROLS

FUEL SYSTEM DIAGNOSIS

Circuit Description

The fuel pump is an in-tank type mounted to a fuel send-
er assembly. The fuel pump will remain on as long as the
engine is cranking or running and the Engine Control
Module (ECM) is receiving reference pulses from the
crankshaft position (CKP) sensor. If there are no refer-
ence pulses, the ECM will turn off the fuel pump two sec-
onds after the ignition switch is turned ON or two
seconds after the engine stops running. The fuel pump
delivers fuel to the fuel rail and the fuel injectors, where
the fuel system pressure is controlled from 380 kPa (55
psi) by the fuel pressure regulator. The excess fuel is re-
turned to the fuel tank.

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 pres-
sure before disconnecting the fuel lines.

Caution: Do not pinch or restrict nylon fuel lines.
Damage to the lines could cause a fuel leak, result-
ing in possible fire or personal injury.

Fuel Pressure Relief Procedure

1. Remove the fuel cap.

2. Remove the fuel pump fuse EF23 from the engine

fuse block.

3. Start the engine and allow the engine to stall.

4. Crank the engine for an additional 10 seconds.

Fuel System Pressure Test

ÁÁÁÁ

Step

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Action

ÁÁÁÁÁ

Value(s)

ÁÁÁÁÁÁÁ

Yes

ÁÁÁÁÁÁ

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

1. Relieve the fuel system pressure.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure around the values specified and
holding steady?

ÁÁÁÁÁ

380 kPa

(55 psi)

ÁÁÁÁÁÁÁ

System OK

ÁÁÁÁÁÁ

Go to Step 2

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

1. Relieve the fuel system pressure.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure around the values specified but
not holding steady?

ÁÁÁÁÁ

380 kPa

(55 psi)

ÁÁÁÁÁÁÁ

Go to Step 13

ÁÁÁÁÁÁ

Go to Step 3

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

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

ÁÁÁÁÁ

–

ÁÁÁÁÁÁÁ

Go to Step 4

ÁÁÁÁÁÁ

Go to Step 5

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

1. Replace the fuel line(s) as needed.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure around the values specified and
holding steady?

ÁÁÁÁÁ

380 kPa

(55 psi)

ÁÁÁÁÁÁÁ

System OK

ÁÁÁÁÁÁ

–

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

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?

ÁÁÁÁÁ

–

ÁÁÁÁÁÁÁ

Go to Step 6

ÁÁÁÁÁÁ

Go to Step 7

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

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 around the values specified and
holding steady?

ÁÁÁÁÁ

380 kPa

(55 psi)

ÁÁÁÁÁÁÁ

System OK

ÁÁÁÁÁÁ

Go to Step 8

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

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

ÁÁÁÁÁ

–

ÁÁÁÁÁÁÁ

Go to Step 8

ÁÁÁÁÁÁ

Go to Step 9

ENGINE CONTROLS 1F – 35

Fuel System Pressure Test (Cont’d)

ÁÁÁÁ

Step

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Action

ÁÁÁÁÁ

Value(s)

ÁÁÁÁÁÁÁ

Yes

ÁÁÁÁÁÁ

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

1. Replace the fuel pressure regulator.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure around the values specified and
holding steady?

ÁÁÁÁÁ

380 kPa

(55 psi)

ÁÁÁÁÁÁÁ

System OK

ÁÁÁÁÁÁ

–

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

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

ÁÁÁÁÁ

–

ÁÁÁÁÁÁÁ

Go to Step 10

ÁÁÁÁÁÁ

Go to Step 11

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

1. Replace the fuel pump assembly.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure around the values specified and
holding steady?

ÁÁÁÁÁ

380 kPa

(55 psi)

ÁÁÁÁÁÁÁ

System OK

ÁÁÁÁÁÁ

–

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

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?

ÁÁÁÁÁ

–

ÁÁÁÁÁÁÁ

Go to Step 12

ÁÁÁÁÁÁ

–

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

1. Replace the leaking fuel injector(s).
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure around the values specified and
holding steady?

ÁÁÁÁÁ

380 kPa

(55 psi)

ÁÁÁÁÁÁÁ

System OK

ÁÁÁÁÁÁ

–

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

1. Replace the fuel pressure regulator.
2. Start the engine.
3. Allow the engine to idle.
Is the fuel pressure around the values specified and
holding steady?

ÁÁÁÁÁ

380 kPa

(55 psi)

ÁÁÁÁÁÁÁ

System OK

ÁÁÁÁÁÁ

–

1F – 36 ENGINE CONTROLS

MAA1F040

FUEL PUMP RELAY CIRCUIT CHECK

Circuit Description

When the ignition switch is turned ON, the Engine Con-
trol Module (ECM) will supply battery voltage to activate
the fuel pump relay and run the in-tank fuel pump. The
fuel pump will operate as long as the engine is cranking
or running and the ECM is receiving ignition reference
pulses.

If there are no reference pulses, the 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 con-
nection, rubbed through wire insulation, or a broken wire
inside the insulation.

Fuel Pump Relay Circuit Check

Step

Action

Value(s)

Yes

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

1. Turn the ignition OFF.
2. Connect battery positive to fuel pump test

connect.

3. Listen for in-tank fuel pump operation.
Does the fuel pump operate?

–

Go to Step 4

Go to Step 3

ENGINE CONTROLS 1F – 37

Fuel Pump Relay Circuit Check (Cont’d)

Step

Action

Value(s)

Yes

1. Check for an open circuit between fuel pump test

connector and ground G401, and repair as
needed.

2. Check for the fuel cut-off switch and reset or

replace the fuel cut off switch.

Is the repair complete?

–

System OK

Go to Step 4

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

connector terminal 66 and battery positive.

4. Turn the ignition ON.
Is the test light on?

–

Go to Step 6

Go to Step 5

Check for an open circuit between terminal 66 of fuel
pump relay and battery positive and repair as
needed.
Is the repair complete?

–

System OK

–

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

connector terminal 85 and ground.

3. Turn the ignition ON.
Is the test light on?

2 sec

Go to Step 8

Go to Step 7

Check for an open circuit between terminal 85 of fuel
pump relay and terminal 10 of ECM, and repair as
needed.
Is the repair complete?

–

System OK

–

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 10

Go to Step 9

1. Check the fuse EF19, if blown, repair short circuit

between fuel pump relay 30 terminal.

2. Replace the fuse as needed.
3. Repair an open circuit as needed.
Is the repair complete?

–

System OK

–

1. Turn the ignition OFF.
2. Measure the resistance between following

terminals:

Terminal 87 of fuel pump relay and terminal 1
of the fuel cut-off switch(or terminal 1 of
connector C201).

Does the resistance within the value specified.

Ω

Go to Step 12

Go to Step 11

Repair an open circuit as needed.
Is the repair complete?

–

System OK

–

Replace the fuel pump relay.
Is the repair complete?

–

System OK

Go to Step 13

Replace the ECM.
Is the repair complete?

–

System OK

–

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