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For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2004 🢒 VUE - FWD 🢒 Engine 🢒 Engine Controls - 3.5L (L66) 🢒 Fuel Injector Balance Test with Tech 2
Table 1: Injector Balance Test Example

System Description

The scan tool is first used to energize the fuel pump relay. The scan tool is then used to pulse each injector for a precise amount of time allowing a measured amount of fuel into the manifold. This causes a drop in system fuel pressure that can be recorded and used to compare each injector.

Injector Balance Test Example

Cylinder

1

2

3

4

5

6

1st Reading

365 kPa (53 psi)

365 kPa (53 psi)

365 kPa (53 psi)

365 kPa (53 psi)

365 kPa (53 psi)

365 kPa (53 psi)

2nd Reading

245 kPa (36 psi)

200 kPa (30 psi)

245 kPa (36 psi)

240 kPa (35 psi)

245 kPa (36 psi)

255 kPa (37 psi)

Amount of Drop

120 kPa (17 psi)

165 kPa (23 psi)

120 kPa (17 psi)

125 kPa (18 psi)

120 kPa (17 psi)

110 kPa (16 psi)

Average Range: 117-137 kPa (16.5-19.5 psi)

Injector OK

Faulty injector - too much fuel drop

Injector OK

Injector OK

Injector OK

Faulty injector - too little fuel drop

Test Description

The number below refers to the step number 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. The engine coolant temperature must be less than the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.

    3.

  3. This step checks that the fuel pressure is within the specified operating range of this fuel system.

    4.

  4. This step checks for a steady fuel pressure reading. A steady fuel pressure reading indicates that the fuel system is operating properly.

    5.

  5. The fuel injectors are flowing properly if the pressure drop value for each fuel injector is within 10 kPa (1.5 psi) of the average pressure drop value. Calculate the pressure drop value for each fuel injector by subtracting the second pressure reading from the first pressure reading. Refer to the examples in the preceding table.

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 (ECT) is above 94°C (201°F).

Observe the ECT Sensor parameter with a scan tool.

Is the ECT Sensor parameter less than the specified value?

94°C (201°F)

Go to Step 5

Go to Step 4

4

Allow the engine to cool to less than the specified value.

Is the engine coolant temperature less than the specified value?

94°C (201°F)

Go to Step 5

--

5

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 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 the scan tool. Refer to Scan Tool Output Controls .
  6. Observe the fuel pressure gage, with the fuel pump operating.

Is the fuel pressure within the specified value?

330-382 kPa (48-56 psi)

Go to Step 6

Go to Fuel System Diagnosis

6

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 7

7

Notice: Do Not repeat any portion of this test before running the engine in order to prevent the engine from flooding.

  1. With a scan tool, select the Fuel Injector Balance Test function, within the Special Functions menu.
  2. Select an injector to be tested.
  3. Press Enter. This will prime the fuel system.
  4. Record the fuel pressure indicated by the fuel pressure gage after the fuel pressure stabilizes. This is the 1st 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 Pulse Injector button on the scan tool. This will energize the injector and decrease the fuel pressure. Refer to Scan Tool Output Controls .
  6. Record the fuel pressure indicated by the fuel pressure gage after the fuel injector has stopped pulsing. This is the 2nd pressure reading.
  7. Press Enter again to bring you back to the Select Injector screen.
  8. Repeat for each fuel injector.
  9. Subtract the 2nd pressure reading from the 1st pressure reading for one fuel injector. The result is the pressure drop value.
  10. Obtain a pressure drop value for each fuel injector.
  11. Add all of the individual pressure drop values. This is the total pressure drop.
  12. Divide the total pressure drop by the number of fuel injectors. This is the average pressure drop.

Is the difference between any individual pressure drop and the average pressure drop more than the specified value?

10 kPa (1.5 psi)

Go to Step 8

Go to Symptoms - Engine Controls

8

Replace the affected fuel injectors.

Did you complete the replacement?

--

Go to Step 9

--

9
  1. Start the engine.
  2. Perform the idle learn procedure. Refer to Idle Learn .

Does an engine performance concern still exist?

--

System OK

Go to Symptoms - Engine Controls