GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2004 🢒 L300/LW300 🢒 Engine 🢒 Engine Electrical 🢒 Fuel System Diagnosis

System Description

The control module enables the fuel pump relay when the ignition switch is turned ON. The control module will disable the fuel pump relay within 2 seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump relay as long as ignition reference pulses are detected. The control module disables the fuel pump relay within 2 seconds if ignition reference pulses cease to be detected and the ignition remains ON.

The fuel tank stores the fuel supply. The electric fuel pump supplies fuel through an in-line fuel filter to the fuel injection system. The pump provides fuel at a higher rate of flow than is needed by the fuel injection system. The fuel pressure regulator maintains the correct fuel pressure to the fuel injection system. A separate pipe returns unused fuel to the fuel tank.

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Important: Inspect the fuel system for damage or external leaks before proceeding with this diagnostic.

  1. Turn ON the ignition, with the engine OFF.
  2. Command the fuel pump relay ON with a scan tool.

Does the fuel pump operate?

--

Go to Step 3

Go to Fuel Pump Electrical Circuit Diagnosis

3

Important: Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic.

  1. Turn ON the ignition, with the engine OFF.
  2. Disconnect the fuel pressure regulator vacuum tube.
  3. Command the fuel pump relay ON with a scan tool.
  4. Inspect for a fuel leak from the fuel pressure regulator vacuum port.

Is the fuel pressure regulator leaking fuel?

--

Go to Step 25

Go to Step 4

4
  1. Command the fuel pump relay OFF with a scan tool.
  2. Turn OFF the ignition.
  3. Turn OFF all accessories.
  4. Install the SA9127E Gage Bar Set with the Fuel Pressure Adapter and the Drain Hose. Refer to Fuel Pressure Gage Installation and Removal .
  5. Turn ON the ignition, with the engine OFF.

    6. Important: DO NOT start the engine.

  6. Command the fuel pump relay ON with a scan tool.
  7. Observe the fuel pressure gage with the fuel pump commanded ON.

Is the fuel pressure within the specified range?

345-414 kPa (50-60 psi)

Go to Step 5

Go to Step 9

5

Important: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.

Monitor the fuel pressure gage for 5 minutes.

Does the fuel pressure decrease by more than the specified value?

55 kPa (8 psi)

Go to Step 7

Go to Step 6

6
  1. Operate the vehicle within the conditions to reproduce the original symptoms.
  2. Monitor the O2 and the Fuel Trim parameters with a scan tool.

Do the scan tool parameters indicate a lean condition?

--

Go to Step 13

Go to Symptoms - Engine Controls

7
  1. Turn OFF the ignition.
  2. Relieve the fuel pressure. Refer to Fuel Pressure Relief .
  3. Remove the fuel pressure gage from the fuel pressure test connection.
  4. Disconnect the chassis fuel hoses from the engine compartment fuel pipes. Refer to Metal Collar Quick Connect Fitting Service .
  5. Connect the fuel feed hose to the inlet side of SA9127E-7 Fuel Pressure/Flow Adapter using the J 43937 3/8 inch Male Fuel Pressure Adapter Line.
  6. Connect the fuel return hose to the outlet side of SA9127E-7 using the J 43937 5/16 inch Male Fuel Pressure Adapter Line.
  7. Close the valve on the SA9127E-7 .
  8. Turn ON the ignition, with the engine OFF.
  9. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.
  10. Record the fuel pressure.
  11. Command the fuel pump relay OFF.
  12. Monitor the fuel pressure gage for 5 minutes.

Does the fuel pressure decrease by more than the specified value?

55 kPa (8 psi)

Go to Step 27

Go to Step 8

8
  1. Turn OFF the ignition.
  2. Open the valve on the SA9127E-7 .
  3. Disconnect the fuel feed hose from the inlet side of SA9127E-7 .
  4. Connect the fuel feed hose to the engine compartment fuel pipe. Refer to Metal Collar Quick Connect Fitting Service .
  5. Connect the fuel rail side of the engine compartment fuel return pipe to the inlet side of SA9127E-7 using the J 43937 5/16 inch Female Fuel Pressure Adapter Line.
  6. Close the valve on the SA9127E-7 .
  7. Turn ON the ignition, with the engine OFF.
  8. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.
  9. Record the fuel pressure.
  10. Command the fuel pump relay OFF.
  11. Monitor the fuel pressure gage for 5 minutes.

Does the fuel pressure decrease by more than the specified value?

55 kPa (8 psi)

Go to Step 20

Go to Step 25

9

Is the fuel pressure more than the specified value?

414 kPa (60 psi)

Go to Step 10

Go to Step 13

10
  1. Turn OFF the ignition.
  2. Relieve the fuel pressure. Refer to Fuel Pressure Relief .
  3. Disconnect the fuel return hose from the engine compartment fuel return pipe. Refer to Metal Collar Quick Connect Fitting Service .
  4. Connect the fuel rail side of the engine compartment fuel return pipe to the inlet side of SA9127E-7 using the J 43937 5/16 inch Female Fuel Pressure Adapter Line.
  5. Connect the return hose from the SA9127E-7 to the outlet side of the SA9127E-7 .
  6. Place the other end of the return hose into the fuel filler pipe.
  7. Cap the pressure test port on the SA9127E-7 with the J 43936 Fuel Pressure Adapter Cap.
  8. Open the valve on the SA9127E-7 .
  9. Turn ON the ignition, with the engine OFF.
  10. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.
  11. Monitor the fuel pressure gage while the fuel pump is operating.

Is the fuel pressure less than the specified value?

517 kPa (75 psi)

Go to Step 11

Go to Step 17

11
  1. Turn OFF the ignition.
  2. Relieve the fuel pressure. Refer to Fuel Pressure Relief .
  3. Remove the SA9127E-7 .
  4. Connect the fuel return hose to the engine compartment fuel return pipe. Refer to Metal Collar Quick Connect Fitting Service .
  5. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  6. Disconnect the chassis fuel return pipe at the passenger side front wheel well area. Refer to Plastic Collar Quick Connect Fitting Service .
  7. Connect the engine side of the fuel return pipe to the inlet side of SA9127E-7 using the J 43937 5/16 inch Female Fuel Pressure Adapter Line.
  8. Connect the return hose from the SA9127E-7 to the outlet side of SA9127E-7 .
  9. Place the other end of the return hose into the fuel filler pipe.
  10. Cap the pressure test port on the SA9127E-7 with the J 43936 .
  11. Open the valve on the SA9127E-7 .
  12. Turn ON the ignition, with the engine OFF.
  13. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.
  14. Monitor the fuel pressure gage while the fuel pump is operating.

Is the fuel pressure less than the specified value?

517 kPa (75 psi)

Go to Step 12

Go to Step 22

12
  1. Turn OFF the ignition.
  2. Relieve the fuel pressure. Refer to Fuel Pressure Relief .
  3. Remove the SA9127E-7 .
  4. Connect the chassis fuel return pipe at the passenger side front wheel well area. Refer to Plastic Collar Quick Connect Fitting Service .
  5. Remove the fuel pipe shield.
  6. Disconnect the fuel return pipe at the front of the fuel tank. Refer to Plastic Collar Quick Connect Fitting Service .
  7. Connect the engine side of the fuel return pipe to the inlet side of SA9127E-7 using the J 43937 5/16 inch Female Fuel Pressure Adapter Line.
  8. Connect the return hose from the SA9127E-7 to the outlet side of SA9127E-7 .
  9. Place the other end of the return hose into the fuel filler pipe.
  10. Cap the pressure test port on the SA9127E-7 with the J 43936 .
  11. Open the valve on the SA9127E-7 .
  12. Turn ON the ignition, with the engine OFF.
  13. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.
  14. Monitor the fuel pressure gage while the fuel pump is operating.

Is the fuel pressure less than the specified value?

517 kPa (75 psi)

Go to Step 19

Go to Step 24

13
  1. Turn OFF the ignition.
  2. Relieve the fuel pressure. Refer to Fuel Pressure Relief .
  3. Remove the fuel pressure gage from the fuel pressure test connection.
  4. Disconnect the chassis fuel hoses from the engine compartment fuel pipes. Refer to Metal Collar Quick Connect Fitting Service .
  5. Connect the fuel feed hose to the inlet side of SA9127E-7 using the J 43937 3/8 inch Male Fuel Pressure Adapter Line.
  6. Connect the fuel return hose to the outlet side of SA9127E-7 using the J 43937 5/16 inch Male Fuel Pressure Adapter Line.
  7. Connect the fuel pressure gage to the SA9127E-7 .
  8. Open the valve on the SA9127E-7 .
  9. Turn ON the ignition, with the engine OFF.
  10. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.

Is the fuel pressure more than the specified value?

379 kPa (55 psi)

Go to Step 25

Go to Step 14

14
  1. Turn OFF the ignition.
  2. Remove the SA9127E-7 .
  3. Connect the chassis fuel hoses to the engine compartment fuel pipes. Refer to Metal Collar Quick Connect Fitting Service .
  4. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  5. Disconnect the fuel feed pipe at the fuel filter inlet. Refer to Plastic Collar Quick Connect Fitting Service .
  6. Connect the fuel feed pipe to the inlet side of SA9127E-7 using the J 43937 3/8 inch Male Fuel Pressure Adapter Line.
  7. Connect the return hose from the SA9127E-7 to the outlet side of SA9127E-7 .
  8. Place the other end of the return hose into the fuel filler pipe.
  9. Open the valve on the SA9127E-7 .
  10. Turn ON the ignition, with the engine OFF.
  11. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.

Is the fuel pressure more than the specified value?

379 kPa (55 psi)

Go to Step 15

Go to Step 18

15
  1. Turn OFF the ignition.
  2. Remove the SA9127E-7 from the fuel filter inlet.
  3. Connect the fuel feed pipe to the fuel filter inlet. Refer to Plastic Collar Quick Connect Fitting Service .
  4. Disconnect the fuel feed pipe at the fuel filter outlet. Refer to Plastic Collar Quick Connect Fitting Service .
  5. Connect the inlet side of SA9127E-7 to the fuel filter outlet using the J 43937 3/8 inch Female Fuel Pressure Adapter Line.
  6. Open the valve on the SA9127E-7 .
  7. Turn ON the ignition, with the engine OFF.
  8. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.

Is the fuel pressure more than the specified value?

379 kPa (55 psi)

Go to Step 16

Go to Step 26

16
  1. Turn OFF the ignition.
  2. Remove the SA9127E-7 from the fuel filter outlet.
  3. Connect the fuel feed pipe to the fuel filter outlet. Refer to Plastic Collar Quick Connect Fitting Service .
  4. Disconnect the chassis fuel feed pipe at the passenger side front wheel well area. Refer to Plastic Collar Quick Connect Fitting Service .
  5. Connect the fuel tank side of the fuel feed pipe to the inlet side of SA9127E-7 using the J 43937 3/8 inch Male Fuel Pressure Adapter Line.
  6. Open the valve on the SA9127E-7 .
  7. Turn ON the ignition, with the engine OFF.
  8. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.

Is the fuel pressure more than the specified value?

379 kPa (55 psi)

Go to Step 21

Go to Step 23

17

Inspect the fuel rail return pipe and the fuel rail outlet passage for a restriction.

Did you find and correct the condition?

--

Go to Step 28

Go to Step 25

18

Inspect the rear fuel feed pipe on the fuel tank for damage and for a restriction.

Did you find and correct the condition?

--

Go to Step 28

Go to Step 27

19

Inspect the rear fuel return pipe on the fuel tank for a restriction.

Did you find and correct the condition?

--

Go to Step 28

Go to Step 27

20
  1. Turn OFF the ignition.
  2. Open the valve on the SA9127E-7 .
  3. Remove the SA9127E-7 from the fuel return pipe.
  4. Connect the fuel return hose to the engine compartment fuel pipe. Refer to Metal Collar Quick Connect Fitting Service .
  5. Raise the fuel rail, with the fuel lines connected. Refer to Fuel Injection Fuel Rail Assembly Replacement .
  6. Turn ON the ignition, with the engine OFF.
  7. Command the fuel pump relay ON with a scan tool.
  8. Locate and replace the leaking fuel injector. Refer to Fuel Injector Replacement .

Did you complete the replacement?

--

Go to Step 28

--

21

Replace the engine compartment fuel feed pipe. Refer to Fuel Hose/Pipes Replacement - Engine Compartment .

Did you complete the replacement?

--

Go to Step 28

--

22

Replace the engine compartment fuel return pipe. Refer to Fuel Hose/Pipes Replacement - Engine Compartment .

Did you complete the replacement?

--

Go to Step 28

--

23

Replace the chassis fuel feed pipe. Refer to Fuel Hose/Pipes Replacement - Chassis .

Did you complete the replacement?

--

Go to Step 28

--

24

Replace the chassis fuel return pipe. Refer to Fuel Hose/Pipes Replacement - Chassis .

Did you complete the replacement?

--

Go to Step 28

--

25

Important: Inspect for a missing or damaged O-ring seal before replacing the fuel pressure regulator.

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

Did you complete the replacement?

--

Go to Step 28

--

26

Replace the fuel filter. Refer to Fuel Filter Replacement .

Did you complete the replacement?

--

Go to Step 28

--

27

Replace the fuel sender. Refer to Fuel Sender Assembly Replacement .

Did you complete the replacement?

--

Go to Step 28

--

28

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 4