GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 S10 Pickup - 2WD 🢒 Body and Accessories 🢒 Wiring Systems 🢒 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 two 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 two 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 OFF the ignition.
  2. Turn OFF all accessories.
  3. Install a fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal .
  4. Turn ON the ignition, with the engine OFF.

    5. Important: 

       • The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.
       • 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?

379-427 kPa (55-62 psi)

Go to Step 4

Go to Step 9

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 1 minute.

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

34 kPa (5 psi)

Go to Step 7

Go to Step 5

5
  1. Relieve the fuel pressure to the first specified value.
  2. Monitor the fuel pressure gage for 5 minutes.

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

69 kPa (10 psi)

14 kPa (2 psi)

Go to Step 17

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 12

Go to Symptoms - Engine Controls

7

  1. Turn OFF the ignition.
  2. Relieve the fuel pressure. Refer to Fuel Pressure Relief .
  3. Disconnect the fuel feed hose from the fuel rail. Refer to Metal Collar Quick Connect Fitting Service .
  4. Install the J 37287 Fuel Line Shut-off Adapter between the fuel hose and the fuel rail.
  5. Open the valve on the fuel pipe shut-off adapter.
  6. Turn ON the ignition, with the engine OFF.
  7. Command the fuel pump relay ON with a scan tool.
  8. Bleed the air from the fuel pressure gage.
  9. Command the fuel pump relay ON and then OFF with a scan tool.
  10. Close the fuel feed pipe shut-off valve.
  11. Monitor the fuel pressure gage for 1 minute.

Does the fuel pressure remain constant?

--

Go to Step 8

Go to Step 15

8
  1. Turn OFF the ignition.
  2. Open the fuel feed pipe shut-off valve.
  3. Relieve the fuel pressure. Refer to Fuel Pressure Relief .
  4. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  5. Disconnect the fuel return pipe from the fuel filter. Refer to Plastic Collar Quick Connect Fitting Service .
  6. Install the J 37287 between the fuel return pipe and the fuel filter.
  7. Open the fuel return pipe shut-off valve.
  8. Turn ON the ignition, with the engine OFF.
  9. Command the fuel pump relay ON with a scan tool.
  10. Bleed the air from the fuel pressure gage.
  11. Command the fuel pump relay ON and then OFF with a scan tool.
  12. Close the fuel return pipe shut-off valve.
  13. Monitor the fuel pressure gage for 1 minute.

Does the fuel pressure remain constant?

--

Go to Step 16

Go to Step 17

9

Is the fuel pressure more than the specified value?

427 kPa (62 psi)

Go to Step 11

Go to Step 10

10

  1. Turn OFF the ignition.
  2. Relieve the fuel pressure. Refer to Fuel Pressure Relief .
  3. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  4. Disconnect the fuel return pipe from the fuel filter. Refer to Plastic Collar Quick Connect Fitting Service .
  5. Install the J 37287 between the fuel return pipe and the fuel filter.
  6. Open the valve in the fuel pipe shut-off adapter.
  7. Turn ON the ignition, with the engine OFF.
  8. Bleed the air from the fuel pressure gage.
  9. Monitor the fuel pressure gage.

    10. Notice: DO NOT allow the fuel pressure to exceed 517 kPa (75 psi). Excessive pressure may damage the fuel system.

  10. Command the fuel pump relay ON with a scan tool.
  11. Slowly close the valve in the fuel return pipe shut-off adapter, while the fuel pump is operating.

Does the fuel pressure increase to more than the specified value?

427 kPa (62 psi)

Go to Step 16

Go to Step 12

11

Inspect the fuel return pipe for a restriction.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 16

12

Inspect the following components for a restriction:

    • The fuel filter
    • The fuel feed pipe

Did you find and correct the condition?

--

Go to Step 18

Go to Step 13

13

Inspect the harness connectors and the ground circuits of the fuel pump for poor connections. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 14

14

  1. Remove the fuel sender assembly. Refer to Fuel Sender Assembly Replacement .
  2. Inspect the following items:
    3. • The fuel pump flex hose for damage
    • The in-tank fuel pump harness connectors for poor connections
    • The fuel strainer for a restriction
    • The fuel tank for contaminants

Did you find and correct the condition?

--

Go to Step 18

Go to Step 17

15

  1. Turn OFF the ignition.
  2. Raise the fuel rail with the fuel pipe connected. Refer to Fuel Injection Fuel Rail Assembly Replacement .
  3. Turn ON the ignition, with the engine OFF.
  4. Command the fuel pump relay ON with a scan tool.
  5. Locate and replace the leaking fuel injector. Refer to Fuel Injector Replacement .

Did you complete the replacement?

--

Go to Step 18

--

16

Replace the fuel filter. Refer to Fuel Filter Replacement .

Did you complete the replacement?

--

Go to Step 18

--

17

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

Did you complete the replacement?

--

Go to Step 18

--

18

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3