GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1996 🢒 Riviera 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Fuel Injector Balance Test

Test Description

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.

  1. The engine coolant temperature must be below the operating temperature in order to avoid irregular fuel pressure readings due to Hot Soak fuel boiling.

    2.

  2. The fuel pressure should be within the specified range. If the fuel pressure is not within the specified range, go to Fuel System Diagnosis

  3. The fuel pressure should reach a steady value. If the fuel pressure does not reach a steady value, go to Fuel System Diagnosis

  4. 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 illustration above.

Test Procedure

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Was the Fuel Injector Coil Test Procedure performed?

--

Go to Step 3

Go to Fuel Injector Solenoid Coil Test

3

Is the engine coolant temperature above the specified value?

94°C (201°F)

Go to Step 4

Go to Step 5

4

Allow the engine to cool below the specified value.

Is the engine coolant temperature below the specified value?

94°C (201°F)

Go to Step 5

--

5

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.

  1. Install the fuel pressure gauge.
  2. Energize the fuel pump using the scan tool.
  3. Place the bleed hose of the fuel pressure gauge into an approved gasoline container.
  4. Bleed the air out of the fuel pressure gauge.
  5. Using a scan tool pressurize the fuel system.
  6. Wait for the fuel pressure to build.

    7. Important: The fuel pump will run for approximately 2 seconds. Repeat Step 4 as necessary in order to achieve the highest possible fuel pressure.

  7. Observe the reading on the fuel pressure gauge.

Is the fuel pressure within the specified limits?

333-376 kPa (48-55 psi)

Go to Step 6

Go to Fuel System Diagnosis

6

Turn the fuel pump OFF.

Does the fuel pressure remain constant?

--

Go to Step 7

Go to Fuel System Diagnosis

7

  1. Connect the J 39021 fuel injector tester to a fuel injector.
  2. Set the amperage supply selector switch on the fuel injector tester to the Balance Test 0.5-2.5 amp position.
  3. Turn the fuel pump ON then OFF in order to pressurize the fuel system.
  4. Record the fuel pressure indicated by the fuel pressure gauge after the fuel pressure stabilizes. This is the 1st pressure reading.
  5. Energize the fuel injector by depressing the Push to Start Test button on the fuel injector tester.
  6. Record the fuel pressure indicated by the fuel pressure gauge after the fuel pressure gauge needle has stopped moving. This is the 2nd pressure reading.
  7. Repeat Steps 1 through 6 for each fuel injector.
  8. Subtract the 2nd pressure reading from the 1st 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 either higher than the average pressure drop or lower than the average pressure drop by the specified value?

10 kPa (1.5 psi)

Go to Step 8

Go to Symptoms, Section

8

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

Re-test any fuel injector that does not meet the specification. Refer to the procedure in Step 7.

Does any fuel injector still have a pressure drop value that is either higher than the average pressure drop or lower than the average pressure drop by the specified value?

10 kPa (1.5 psi)

Go to Step 9

Go to Symptoms, Section

9

Replace the faulty fuel injector(s). Refer to Fuel Injector Replacement

Is the action complete?

--

System OK

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