GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2002 🢒 Corvette 🢒 Body and Accessories 🢒 Wiring Systems 🢒 Fuel System Diagnosis

Circuit Description

When you turn ON the ignition switch, the control module enables the fuel pump relay which powers the fuel pump ON. The fuel pump remains ON as long as the engine is cranking or running and the control module receives ignition reference pulses. If there are no ignition reference pulses, the control module shuts the fuel pump off within 2 seconds after the ignition was switched to the ON position or if the engine stops.

The in-tank fuel pump is an electric pump that is attached to the fuel sender assembly. The fuel pump also supplies fuel to the right fuel tank siphon jet pump. The siphon jet pump transfers fuel from the right fuel tank to the left fuel tank. The fuel pump is designed to provide fuel at a pressure above the pressure that is needed by the fuel injectors. A fuel pressure regulator, which is part of the fuel filter assembly, keeps the fuel available to the fuel injectors at a regulated pressure. Unused fuel is returned to the fuel tank by a separate fuel return pipe.

Test Description

  1. This step verifies that the fuel pump is operating.

    2.

  2. This step verifies that the vehicle is not out of fuel. If the left fuel tank is empty, and there is fuel in the right fuel tank, a fuel transfer condition exists.

    3.

  3. This step tests for an internal fuel leak. If the fuel pressure drops during this test, then an internal loss of pressure is indicated.

    4.

  4. This step tests for a loss of fuel pressure between the fuel feed pipe shut off adapter and the fuel injectors. If the fuel pressure decreases during this test inspect for a leaking fuel injector.

    5.

  5. This step tests for a loss of fuel pressure between the fuel feed pipe shut off adapter and the fuel pump. If the fuel pressure remains constant with the shut off valve closed, the loss of fuel pressure is caused by the fuel pump.

    6.

  6. This step tests if the loss of fuel pressure is caused by the fuel pressure regulator, or by the check valve that is located in the fuel feed rear pipe.

    7.

  7. This step determines if the fuel pressure regulator, or the fuel pump is the cause of the low fuel pressure. If the pressure rises above the specified value, the fuel pump is OK.

    8.

  8. This step verifies that there is an adequate supply of fuel to the siphon jet pump.

    9.

  9. This step verifies the fuel return from the siphon jet pump. If the fuel returned is near the specified value, inspect the left fuel sender for blockage.

    10.

  10. This step verifies that a circuit condition is not the cause of a fuel pressure concern. Inspect all fuel pump electrical circuits thoroughly.

Step

Action

Value(s)

Yes

No

System Reference: Fuel System Description

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 for external leaks, before proceeding with this diagnostic.

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

Does the fuel pump operate?

--

Go to Step 3

Go to Fuel Pump Electrical Circuit Diagnosis

3

Monitor the left fuel sender voltage with a scan tool.

Is the left fuel sender voltage less than the specified value?

0.8 V

Go to Step 4

Go to Step 6

4

Monitor the right fuel sender voltage with a scan tool.

Is the right fuel sender voltage less than the specified value?

0.8 V

Go to Step 5

Go to Step 16

5
  1. Add the specified amount of fuel.
  2. Operate the vehicle within the conditions of the customers concern.

Does a driveability condition still exist?

19 liters (5 gallons)

Go to Step 6

Go to Step 29

6
  1. Turn OFF the ignition.
  2. Turn OFF all accessories.

    3. Caution: Wrap a shop towel around the fuel pressure connection in order to reduce the risk of fire and personal injury. The towel will absorb any fuel leakage that occurs during the connection of the fuel pressure gage. Place the towel in an approved container when the connection of the fuel pressure gage is complete.

  3. Install the J 34730-1A fuel pressure gage.
  4. Place the bleed hose of the fuel pressure gage into an approved gasoline container.
  5. Turn ON the ignition, with the engine OFF.
  6. Command the fuel pump ON with a scan tool.
  7. Bleed the air out of the fuel pressure gage.

    8. Important: 

       • You may need to command the fuel pump ON a few times in order to obtain the highest possible fuel pressure.
       • Do not start the engine.

  8. Observe the fuel pressure gage, with the fuel pump commanded ON.

Is the fuel pressure within the specified value?

384-425 kPa (55-62 psi)

Go to Step 7

Go to Step 13

7

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

Monitor the fuel pressure gage for 1 minute.

Does the fuel pressure drop more than the specified value?

34 kPa (5 psi)

Go to Step 10

Go to Step 8

8
  1. Relieve the fuel pressure to the first specified value. Refer to Fuel Pressure Relief .
  2. Monitor the fuel pressure gage for 5 minutes.

Does the fuel drop more than the second specified value?

69 kPa (10 psi)

14 kPa (2 psi)

Go to Step 28

Go to Step 9

9
  1. Operate the vehicle within the conditions of the customer's concern.
  2. Monitor the fuel related parameters with a scan tool.

Do any of the scan tool parameters indicate a lean condition?

--

Go to Step 19

Go to Symptoms - Engine Controls

10

  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 pipe. Refer to Metal Collar Quick Connect Fitting Service .
  4. Install the J 37287 fuel pipe shut off adapter between the fuel hose and the fuel rail pipe.
  5. Open the valve on the fuel feed pipe shut off adapter.
  6. Command the fuel pump ON with a scan tool.
  7. Bleed the air from the fuel pressure gage.
  8. Command the fuel pump ON and then OFF with a scan tool.
  9. Close the fuel feed pipe shut off valve.
  10. Monitor the fuel pressure gage for 1 minute.

Does the fuel pressure remain constant?

--

Go to Step 11

Go to Step 23

11

  1. Turn OFF the ignition.
  2. Relieve the fuel pressure. Refer to Fuel Pressure Relief .
  3. Remove the fuel feed pipe shut off adapter from the fuel rail.
  4. Install the fuel feed hose to the fuel rail pipe.
  5. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  6. Disconnect the fuel feed rear pipe from the left fuel sender. Refer to Fuel Hose/Pipes Assembly Replacement .
  7. Install the J 37287 fuel pipe shut off adapter between the fuel feed rear pipe and the left fuel sender.
  8. Open the valve in the fuel feed pipe shut off adapter.
  9. Turn ON the ignition with the engine OFF.
  10. Command the fuel pump ON with a scan tool.
  11. Bleed the air from the fuel pressure gage.
  12. Command the fuel pump ON and then OFF with a scan tool.
  13. Close the fuel feed pipe shut off valve.
  14. Monitor the fuel pressure gauge for 1 minute.

Does the fuel pressure remain constant?

--

Go to Step 28

Go to Step 12

12

  1. Turn OFF the ignition.
  2. Open the valve in the fuel feed shut off adapter.
  3. Relieve the fuel pressure. Refer to Fuel Pressure Relief .
  4. Disconnect the fuel return rear pipe from the left fuel sender. Refer to Fuel Hose/Pipes Assembly Replacement .
  5. Install the J 37287 fuel pipe shut off adapter between the fuel return rear pipe and the left fuel sender.
  6. Open the valve in the fuel return pipe shut off adapter.
  7. Turn ON the ignition with the engine OFF.
  8. Command the fuel pump ON with a scan tool.
  9. Bleed the air from the fuel pressure gage.
  10. Command the fuel pump ON and then OFF with a scan tool.
  11. Close the fuel return pipe shut off valve.
  12. Monitor the fuel pressure gage for 1 minute.

Does the fuel pressure remain constant?

--

Go to Step 25

Go to Step 26

13

Is the fuel pressure above the specified value?

425 kPa (62 psi)

Go to Step 14

Go to Step 15

14

Inspect the fuel return rear pipe for a restriction. Refer to Fuel System Description .

Did you find and correct the condition?

--

Go to Step 29

Go to Step 25

15

  1. Turn OFF the ignition.
  2. Relieve the fuel pressure. Refer to Fuel Pressure Relief .
  3. Disconnect the fuel return rear pipe from the left fuel sender. Refer to Fuel Hose/Pipes Assembly Replacement .
  4. Install the J 37287 fuel pipe shut off adapter between the fuel return rear pipe and the left fuel sender.
  5. Open the valve in the fuel pipe shut off adapter.
  6. Turn ON the ignition with the engine OFF.
  7. Command the fuel pump ON with a scan tool.
  8. Bleed the air from the fuel system.
  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. Slowly close the valve in the fuel pipe shut off adapter.
  11. Command the fuel pump ON with a scan tool.

Does the fuel pressure rise above the specified value?

425 kPa (62 psi)

Go to Step 25

Go to Step 20

16

    Important: DO NOT add more than 15 liters (4 gallons) of fuel.

  1. Add fuel to the left fuel tank.
  2. Disconnect the auxiliary fuel feed rear pipe from the right fuel sender. Refer to Fuel Hose/Pipes Assembly Replacement .
  3. Insert the auxiliary fuel feed rear pipe into an approved gasoline container.

    4. Important: You may need to command the fuel pump ON a few times in order to obtain the specified time limit.

  4. Command the fuel pump ON for the specified time with a scan tool.
  5. Measure the volume of fuel.

Is the volume of fuel greater than the specified value?

10 seconds

300 ml   (0.633 pt)

Go to Step 17

Go to Step 24

17

Important: Inspect the auxiliary fuel feed rear pipe if the right fuel tank is empty. Fuel flow to the right fuel tank is decreased during fueling if the crossover hose is collapsed or restricted.

  1. Connect the auxiliary fuel feed rear pipe to the right fuel sender.
  2. Disconnect the auxiliary fuel return rear pipe from the left fuel sender. Refer to Fuel Hose/Pipes Assembly Replacement .
  3. Insert the auxiliary fuel return rear pipe into an approved gasoline container.
  4. Command the fuel pump ON for the specified time with the scan tool.
  5. Measure the volume of fuel.

Is the volume of fuel greater than the specified value?

8 seconds

332.6 ml  (0.703 pt)

Go to Step 22

Go to Step 18

18

Inspect the auxiliary fuel return rear pipe for a restriction.

Did you find and correct the condition?

--

Go to Step 29

Go to Step 27

19

Inspect the following components for a restriction:

    • The fuel filter
    • The fuel feed pipe
    • The fuel feed rear pipe

Did you repair the condition?

--

Go to Step 29

Go to Step 28

20

Inspect the harness connectors and 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 29

Go to Step 21

21
  1. Remove the left 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
    • Contaminants in the fuel tank

Did you find and correct the condition?

--

Go to Step 29

Go to Step 28

22

Repair the restriction in the left fuel sender assembly.

Did you complete the action?

--

Go to Step 29

--

23
  1. Turn OFF the ignition.
  2. Raise the fuel rail, with the fuel lines connected. Refer to Fuel Injection Fuel Rail Assembly Replacement .
  3. Turn ON the ignition with the engine OFF.
  4. Command the fuel pump 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 29

--

24

Locate and repair the restriction the following:

    • The orifice located in the tee of the fuel feed rear pipe.
    • The auxiliary fuel feed rear pipe from the tee to the right fuel sender.

Did you complete the action?

--

Go to Step 29

--

25

Replace the fuel filter/regulator assembly. Refer to Fuel Filter Replacement .

Is the replacement complete?

--

Go to Step 29

--

26

Replace the fuel feed rear pipe with check valve. Refer to Fuel Hose/Pipes Assembly Replacement .

Did you complete the action?

--

Go to Step 29

--

27

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

--

Go to Step 29

--

28

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

Is the replacement complete?

--

Go to Step 29

--

29

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3