GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2006 🢒 Terraza Ext. 🢒 Brakes 🢒 Hydraulic Brakes 🢒 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 system is a returnless on-demand design. The fuel pressure regulator is a part of the primary fuel tank module, eliminating the need for a return pipe from the engine. A returnless fuel system reduces the internal temperature of the fuel tank by not returning hot fuel from the engine to the fuel tank. Reducing the internal temperature of the fuel tank results in lower evaporative emissions.

An electric turbine style fuel pump attaches to the primary fuel tank module inside the fuel tank. The fuel pump supplies high pressure fuel through the fuel filter, past the fuel pressure regulator, and through the fuel feed pipe to the fuel injection system. The fuel pressure regulator has a T-joint that diverts the needed fuel to the fuel rail with the unused fuel dropping back into the reservoir of the primary fuel tank module. The primary fuel tank module contains a reverse flow check valve. The check valve and the fuel pressure regulator maintain fuel pressure in the fuel feed pipe and the fuel rail in order to prevent long cranking times.

The primary fuel tank module also contains a primary jet pump and a secondary jet pump. Fuel pump flow loss, caused by vapor expulsion in the pump inlet chamber, is diverted to the primary jet pump and the secondary jet pump through a restrictive orifice located on the pump cover. The primary jet pump fills the reservoir of the primary fuel tank module. The secondary jet pump creates a venturi action which causes the fuel to be drawn from the secondary side of the fuel tank, through the fuel transfer pipe, to the primary side of the fuel tank.

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

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 OFF the ignition.
  2. Turn OFF all accessories.
  3. Install the SA9127E Gage Bar Set with the Fuel Pressure Adapter and the Drain Hose. Refer to Fuel Pressure Gage Installation and Removal .
  4. Turn ON the ignition, with the engine OFF.

    5. Important: DO NOT start the engine.

  5. Command the fuel pump relay ON with a scan tool.
  6. 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 4

Go to Step 7

4

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 6

Go to Step 5

5
  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 8

Go to Symptoms - Engine Controls

6
  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 hose from the engine compartment fuel pipe.
  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 return hose from the SA9127E-7 to the outlet side of SA9127E-7 .
  7. Place the other end of the return hose into the fuel filler pipe.
  8. Connect the fuel pressure gage to the SA9127E-7 .
  9. Close 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.
  12. Record the fuel pressure.
  13. Command the fuel pump relay OFF.
  14. 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 11

Go to Step 9

7

Is the fuel pressure more than the specified value?

414 kPa (60 psi)

Go to Step 11

Go to Step 8

8
  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. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  5. Disconnect the chassis fuel feed pipe at the fuel tank pipe.
  6. Connect the inlet side of SA9127E-7 to the fuel tank pipe using the J 43937 3/8-Inch Female Fuel Pressure Adapter Line.
  7. Place the return hose from the SA9127E-7 into the fuel filler pipe.
  8. Connect the fuel pressure gage to the SA9127E-7 .
  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 10

Go to Step 11

9
  1. Turn OFF the ignition.
  2. Open the valve on the SA9127E-7 .
  3. Remove the SA9127E-7 .
  4. Connect the chassis fuel hose to the engine compartment fuel pipe.
  5. Raise the fuel rail, with the fuel line 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 12

--

10

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

Did you complete the replacement?

--

Go to Step 12

--

11

Replace the primary fuel tank module. Refer to Fuel Sender Assembly Replacement .

Did you complete the replacement?

--

Go to Step 12

--

12

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3