SsangYong Musso. Manual - part 115

1F-44 ENGINE CONTROLS

SSANGYONG Y158

System Description

The fuel pump is an in-tank fuel pump mounted to a fuel
sender 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
reference pulses, the ECM will turn off the fuel pump
one 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 form 320
to 380 kPa (46 to 55 psi) by the fuel pressure regulator.

The excess fuel is returned to the fuel tank.

Test Description
Number(s) below refer to the step(s) number 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 lowing
the fuel pressure.

10. If there is fuel bleeding back through the fuel return

outlet, this is due to a faulty fuel pressure regulator.

FUEL SYSTEM DIAGNOSIS

12. Fuel leaking from the fuel pump inlet is due to a

faulty one-way check valve in the fuel pump.

14. Another symptom often present when the fuel injec-

tors are leaking is hard starting. Leaking fuel injec-
tors can cause a flooding condition.

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.
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 Ef11 form the engine

fuse box.

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

4. Crank the engine for an additional 10 seconds.

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 and
holding steady?
1. Disconnect the fuel pressure regulator vacuum hose.
2. Start the engine.
3. Allow the engine to idle.
4. Connect the fuel pressure regulator vacuum hose.
Did the fuel pressure decrease?
1. 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 60 - 70 kPa (18 - 21 in. Hg) of vacuum to the

fuel pressure regulator.

Did the fuel pressure decrease?

Step

Action

Value(s)

Yes

Fuel System Diagnosis

320 - 380 kPa

(46 - 55 psi)

Go to Step 2

Go to Step 5

System OK

Go to Step 3

Go to Step 4

Go to Step 16

ENGINE CONTROLS 1F-45

SSANGYONG Y158

1. Locate and correct the cause of the vacuum restric-

tion to the fuel pressure regulator.

2. Confirm the operation of the fuel pressure regulator.
Is the repair complete?
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?
Inspect the fuel lines for a leak.
Is the problem found?
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 and
holding steady?
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?
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 and
holding steady?
With the fuel system under pressure, inspect the fuel
return outlet for leaking.
Is the problem found?
1. Repair the fuel return outlet for leaking.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure within the values specified and
holding steady?
With the fuel system under pressure, inspect the fuel
inlet for leaking.
Is the problem found?
1. Repair the fuel inlet for leaking.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure within the values specified and
holding steady?
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?

Step

Action

Value(s)

Yes

Fuel System Diagnosis (Cont’d)

320 - 380 kPa

(46 - 55 psi)

Go to Step 6

Go to Step 17

System OK

Go to Step 7

Go to Step 8

320 - 380 kPa

(46 - 55 psi)

System OK

Go to Step 9

Go to Step 10

320 - 380 kPa

(46 - 55 psi)

System OK

Go to Step 11

Go to Step 12

320 - 380 kPa

(46 - 55 psi)

System OK

Go to Step 13

Go to Step 14

320 - 380 kPa

(46 - 55 psi)

System OK

Go to Step 15

1F-46 ENGINE CONTROLS

SSANGYONG Y158

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 and
holding steady?
1. Replace the fuel pressure regulator.
2. Start the engine.
3. Allow the engine to idle.
4. Connect the fuel pressure regulator vacuum hose.
Did the fuel pressure decrease?
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 specified
and holding steady?
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 specified
and not holding steady?
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 and
holding steady?

Step

Action

Value(s)

Yes

Fuel System Diagnosis (Cont’d)

320 - 380 kPa

(46 - 55 psi)

System OK

320 - 380 kPa

(46 - 55 psi)

Go to Step 19

Go to Step 18

320 - 380 kPa

(46 - 55 psi)

Go to Step 6

320 - 380 kPa

(46 - 55 psi)

System OK

ENGINE CONTROLS 1F-47

SSANGYONG Y158

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