GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC C-Series Medium Duty Truck B7 🢒 Engine 🢒 Engine Controls - 7.4L 🢒 Fuel Injector Solenoid Coil Test

Object Number: 35909 Size: MF

Test Description

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

  1. This step is the setup step for performing the injector coil test. Also read the instructions included with the tools used for this test.

    2.

  2. Engine coolant temperature affects the tool's ability to detect a faulty injector. If the engine coolant temperature is not between 50°F and 95°F, allow the vehicle to warm or cool as necessary.

    3.

  3. Due to a current surge, the first second of the voltage reading may be inaccurate; therefore, begin recording after the first second of the voltage reading. The voltage specification should be within range. The voltage reading may increase throughout the test as the injector windings warm up and the resistance changes. An erratic voltage reading (one that jumps up and down) would indicate an intermittent connection within the fuel 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 engine.
  2. Relieve the fuel pressure. Refer to Fuel Pressure Relief .
  3. Connect the fuel injector tester J 39021 to B+.
  4. Connect the injector switch box J 39021-210 .
  5. Set the amperage supply selection to the 0.5 amp position.
  6. Connect the injector harness connector J 39021-303 .
  7. Connect the leads from J 39200 digital volt meter (DVM to the tenths scale (0.0).
  8. Connect the scan tool.
  9. Monitor the engine coolant temperature.

Is the engine coolant temperature within the specified value?

10°-35°C

Go to Step 4

Go to Step 3

3

Allow the engine to warm or cool as necessary.

Is the engine coolant temperature within the specified value?

10°-35°C

Go to Step 4

--

4

Important: Perform the following test for each injector.

  1. Press the Push To Start Test button.
  2. Monitor the DVM.

Important: Voltage may climb during the test. Watch for erratic readings (voltage that jumps up and down).

Do any of the injector voltage readings fall outside the specified value?

5.44-7.53 V

Go to Step 5

Go to Sequential Multiport Fuel Injector Balance Test

5

Replace the fuel injector that was not within the specified value. Refer to Fuel Injector Replacement .

Is the action complete?

5.44-7.53 V

Go to Step 6

--

6
  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 7

Go to Step 2

7
  1. Allow the engine to idle until reaching the normal operating temperature.
  2. Select the DTC and the Failed This Ign.

Are any DTCs displayed?

--

Go to the applicable DTC table

Go to Step 8

8

Use the scan tool in order to display the Capture Info and the Review Capture Info function.

Are any DTCs displayed that have not been diagnosed?

--

Go to the applicable DTC table

System OK