GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Vivant 🢒 Engine 🢒 Engine Controls - 2.0L (L34 GMDAT) 🢒 Fuel System Diagnosis

Circuit 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 electronic 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 2 seconds after the ignition switch is turned ON or 2 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 379-393 kPa (55-57 psi) by the fuel pressure regulator. The excess fuel is returned to the fuel tank.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. When the engine is idling, the intake manifold vacuum is high. This vacuum is applied to the fuel pressure regulator diaphragm, offsetting the spring pressure inside the fuel pressure regulator and lowering the fuel pressure.

    2.

  2. If there is bleeding back through the fuel return outlet, this is due to a faulty fuel pressure regulator.

    3.

  3. Another symptom often present when the fuel injectors are leaking is hard starting. Leaking fuel injectors can cause a flooding condition.

    4.

  4. Fuel leaking from the fuel pump inlet is due to a faulty 1-way check valve in the fuel pump.

Step

Action

Values

Yes

No

1
  1. Relieve the fuel system pressure. Refer to Fuel Pressure Relief .
  2. Install a fuel pressure gage.
  3. Turn ON the ignition.

Is the fuel pressure within the values specified and holding steady?

379-393 kPa (55-57 psi)

Go to Step 2

Go to Step 5

2

  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?

--

System OK

Go to Step 3

3
  1. Allow the engine to idle.
  2. Disconnect the vacuum hose from the fuel pressure regulator.
  3. Connect a vacuum pump with a gage to the fuel pressure regulator vacuum port.
  4. Apply 41-47 kPa (5.9-6.8 psi) of vacuum to the fuel pressure regulator.

Did the fuel pressure decrease?

--

Go to Step 4

Go to Step 16

4
  1. Locate and correct the cause of the vacuum restriction to the fuel pressure regulator.
  2. Confirm the operation of the fuel pressure regulator.

Is the repair complete?

--

System OK

--

5
  1. Relieve the fuel system pressure. Refer to Fuel Pressure Relief .
  2. Install a fuel pressure gage.
  3. Turn ON the ignition.

Is the fuel pressure within the values specified but not holding steady?

379-393 kPa (55-57 psi)

Go to Step 6

Go to Step 17

6

Caution: Refer to Nylon Fuel Lines Notice in the Preface section.

Inspect the fuel lines for a leak.

Is the problem found?

--

Go to Step 7

Go to Step 8

7
  1. Replace the fuel lines as needed.
  2. Install a fuel pressure gage.
  3. Turn ON the ignition.

Is the fuel pressure within the values specified but not holding steady?

379-393 kPa (55-57 psi)

System OK

--

8
  1. Remove the fuel pump assembly. Refer to Fuel Pump Replacement .
  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 gage.
  3. Turn ON the ignition.

Is the fuel pressure within the values specified but not holding steady?

379-393 kPa (55-57 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. Refer to Fuel Pressure Regulator Replacement .
  2. Install a fuel pressure gage.
  3. Turn ON the ignition.

Is the fuel pressure within the values specified but not holding steady?

379-393 kPa (55-57 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. Refer to Fuel Pump Replacement .
  2. Install a fuel pressure gage.
  3. Turn ON the ignition.

Is the fuel pressure within the values specified but not holding steady?

379-393 kPa (55-57 psi)

System OK

--

14

  1. Remove the fuel rail and the fuel injectors as an assembly. Refer to Fuel Injection Fuel Rail Assembly Replacement .
  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 injectors. Refer to Fuel Injection Fuel Rail Assembly Replacement .
  2. Install a fuel pressure gage.
  3. Turn ON the ignition.

Is the fuel pressure within the values specified but not holding steady?

379-393 kPa (55-57 psi)

System OK

--

16
  1. Replace the fuel pressure regulator. Refer to Fuel Pressure Regulator Replacement .
  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.

Did the fuel pressure decrease?

--

System OK

--

17
  1. Relieve the fuel system pressure. Refer to Fuel Pressure Relief .
  2. Install a fuel pressure gage.
  3. Turn ON the ignition.

Is the fuel system pressure below the values specified and holding steady?

379-393 kPa (55-57 psi)

Go to Step 13

Go to Step 18

18
  1. Relieve the fuel system pressure. Refer to Fuel Pressure Relief .
  2. Install a fuel pressure gage.
  3. Turn ON the ignition.

Is the fuel system pressure below the values specified and holding steady?

379-393 kPa (55-57 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. Refer to Fuel Pump Replacement .
  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. Refer to Fuel Pump Replacement .
  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. Refer to Fuel Pump Replacement .
  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. Refer to Fuel Injection Fuel Rail Assembly Replacement .
  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