GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1997 🢒 Savana 🢒 Engine 🢒 Engine Controls - 5.0L, 5.7L, and 7.4L 🢒 Fuel Injector Balance Test

Fuel Injector Balance Test SFI


Object Number: 34976 Size: MF

Circuit Description

The Fuel Injector Tester J 39021 , the Injector Switch Box J 39021-210 and the Injector Harness Connector J 39021-301 energize the 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. All injectors should be within the same pressure drop range, the average pressure drop value for all injectors is ±10 kPa (1.5 psi).

Test Description

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

  1. This step checks for the proper fuel pressure.

    2.

  2. This step check for a decrease in the fuel pressure after the energizing each injector.

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
  1. Turn off the ignition.
  2. Connect the fuel pressure gauge J 39021-301 and the injector switch box J 39021-210 .
  3. Turn ON the ignition.
  4. Monitor the fuel pressure gauge, the fuel pressure should measure within the specified value.

Is the fuel pressure within the specified value?

415-455 kPa (60-66 psi)

Go to Step 3

Go to Fuel System Diagnosis

3

    Important: Before energizing each injector, run the fuel pump for 2 seconds.

  1. Energize the fuel injectors one at a time.
  2. Record the fuel pressure after energizing the injectors.

Does the fuel pressure drop approximately the specified value?

10 kPa (1.5 psi)

System OK

Go to Step 4

4

Replace the appropriate injector and poppet nozzle assembly.

Is the action complete?

--

Go to Step 5

--

5
  1. Using the scan tool, select the DTC and the Clear Info.
  2. Attempt to start the engine.

Does the engine start and continue to run?

--

Go to Step 6

Go to Step 2

6
  1. Allow the engine to idle until normal operating temperature is reached.

  2. Select the DTC and the Failed This Ign.

Are any DTCs displayed?

--

Go to The Applicable DTC Table

Go to Step 7

7

Using the scan tool, select the Capture Info and the Review Info.

Are any DTCs displayed that have not been diagnosed?

--

Go to The Applicable DTC Table

System OK

Fuel Injector Balance Test CSFI


Object Number: 34974 Size: MF

Circuit Description

The Fuel Injector Tester J 39021 , the Injector Switch Box J 39021-210 and the Injector Harness Connector J 39021-301 energize the 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. All injectors should be within the same pressure drop range, the average pressure drop value for all injectors is ±10 kPa (1.5 psi).

Test Description

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

  1. This step checks for the proper fuel pressure.

    2.

  2. This step check for a decrease in the fuel pressure after the energizing each injector.

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
  1. Turn off the ignition.
  2. Connect the fuel pressure gauge J 39021-301 and the injector switch box J 39021-210 .
  3. Turn ON the ignition.
  4. Monitor the fuel pressure gauge, the fuel pressure should measure within the specified value.

Is the fuel pressure within the specified value?

415-455 kPa (60-66 psi)

Go to Step 3

Go to Fuel System Diagnosis

3

    Important: Before energizing each injector, run the fuel pump for 2 seconds.

  1. Energize the fuel injectors one at a time.
  2. Record the fuel pressure after energizing the injectors.

Does the fuel pressure drop approximately the specified value?

10 kPa (1.5 psi)

System OK

Go to Step 4

4

Replace the appropriate injector and poppet nozzle assembly.

Is the action complete?

--

Go to Step 5

--

5
  1. Using the scan tool, select the DTC and the Clear Info.
  2. Attempt to start the engine.

Does the engine start and continue to run?

--

Go to Step 6

Go to Step 2

6
  1. Allow the engine to idle until normal operating temperature is reached.

  2. Select the DTC and the Failed This Ign.

Are any DTCs displayed?

--

Go to The Applicable DTC Table

Go to Step 7

7

Using the scan tool, select the Capture Info and the Review Info.

Are any DTCs displayed that have not been diagnosed?

--

Go to The Applicable DTC Table

System OK