GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2003 🢒 L300/LW300 🢒 Engine 🢒 Engine Controls - 3.0L (L81) 🢒 Fuel Injector Balance Test with Special Tool
Table 1: Fuel Injector Balance Test Example (Typical)
Table 2: Fuel Injector Balance Test Procedure

Fuel Injector Balance Test Example (Typical)

Cylinder

1

2

3

4

1st Reading

296 kPa (43 psi)

296 kPa (43 psi)

296 kPa (43 psi)

296 kPa (43 psi)

2nd Reading

131 kPa (19 psi)

117 kPa (17 psi)

124 kPa (18 psi)

145 kPa (21 psi)

Amount of Drop

165 kPa (24 psi)

179 kPa (26 psi)

172 kPa (25 psi)

151 kPa (22 psi)

Average Range: 156-176 kPa (22.5-25.5 psi)

Injector OK

Replace fuel injector - too much fuel pressure drop

Injector OK

Replace fuel injector - too little fuel pressure drop

Test Description

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

  1. The engine coolant temperature (ECT) must be below the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.

    2.

  2. If the pressure drop value for each fuel injector is within 10 kPa (1.5 psi) of the average pressure drop value, the fuel injectors are flowing properly. Calculate the pressure drop value for each fuel injector by subtracting the second pressure reading from the first pressure reading. Refer to the Fuel Injector Balance Test Example.

Fuel Injector Balance Test Procedure

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

Did you perform the Fuel Injector Coil Test?

--

Go to Step 3

Go to Fuel Injector Solenoid Coil Test

3

Important : DO NOT perform this test if the engine coolant temperature is above 94°C (201°F).

Observe the ECT with a scan tool.

Is the ECT less than the specified value?

94°C (201°F)

Go to Step 4

--

4

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

  1. Turn OFF the ignition.
  2. Install the fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal .
  3. Turn ON the ignition, with the engine OFF.

    4. Important: 

       • The fuel pump may need to be commanded ON a few times, in order to obtain the highest possible fuel pressure.
       • DO NOT start the engine.

  4. Command the fuel pump ON with a scan tool.
  5. Observe the fuel pressure gage, with the fuel pump commanded ON.

Is the fuel pressure within the specified range?

337-379 kPa (49-55 psi)

Go to Step 5

Go to Fuel System Diagnosis

5

Important: The fuel pressure will drop 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 Fuel System Diagnosis

Go to Step 6

6

  1. Connect the SA9182E Fuel Injector Tester, J 39021-210 Injector Selector Switch Box, EL-39021-461 Adapter Box to the fuel injector harness multi-way connector.
  2. Set the pulse range to 100 on the fuel injector tester.
  3. Command the fuel pump ON and then OFF with a scan tool.
  4. Record the fuel pressure indicated by the fuel pressure gage after the fuel pressure stabilizes. This is the first pressure reading.

    5. Important: Record the fuel pressure value immediately after the fuel injector stops pulsing. The fuel pressure may rise after the fuel injector stops pulsing. DO NOT record the higher fuel pressure value.

  5. Energize the fuel injector by depressing the Activate Injector button on the fuel injector tester.
  6. Record the fuel pressure indicated by the fuel pressure gage after the fuel injector stops pulsing. This is the second fuel pressure reading.
  7. Repeat steps 1 through 6 for each fuel injector.
  8. Subtract the second pressure reading from the first pressure reading for one fuel injector. The result is the pressure drop value.
  9. Obtain a pressure drop value for each fuel injector.
  10. Add all of the individual pressure drop values. This is the total pressure drop.
  11. Divide the total pressure drop by the number of fuel injectors. This is the average pressure drop.

Does any fuel injector have a pressure drop value that is more than the average pressure drop or less than the average pressure drop by the specified value?

10 kPa (1.5 psi)

Go to Step 7

Go to Symptoms - Engine Controls

7

Replace the affected fuel injector. Refer to Fuel Injector Replacement and Fuel Injection Fuel Rail Assembly Replacement .

Did you complete the replacement?

--

Go to Step 8

--

8

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Symptoms - Engine Controls