Century V6-3100 3.1L VIN M SFI (1998)
Fuel Injector: All Technical Service Bulletins
Injector Balance Test
The following tools or their equivalent are required:
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J 39021 Fuel Injector Coil/Balance Tester
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J 39021-210 Fuel Injector Selector Adapter Box
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J 39021-306 Fuel Injector Test Harness
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J 35800-A Fuel Injector Cleaner
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Two pre-measured GM Top-Engine Cleaner Containers, 24 ml (0.812 oz) each, P/N 12346535, U.S. USAGE ONLY. In Canada, use P/N 992872,
443.6 ml (15 oz) bottle. It will be necessary to measure and dispense 48 ml (1.6 oz) of Top Engine-Cleaner into the J 35800-A, injector cleaning
tool. See Injector Cleaning Procedure below for further information.
1.
Disconnect the 10-pin fuel rail electrical connector. Refer to the appropriate Service Information Manual for connector location.
2.
Connect the J 39021, fuel injector coil/balance tester, to the J 39021-210, fuel injector selector adapter box.
3.
Connect the J 39021-306, fuel injector test harness, to the engine 10-pin fuel rail electrical connector. This allows you to test the fuel injectors
without removing the upper intake plenum.
4.
Using the injector tester, J 39021, perform an injector balance test. Use the J 39021-210 to select each individual injector. Record the pressure
drop of each injector.
5.
Subtract the lowest pressure drop, leanest injector, from the highest pressure drop, richest injector. If there is more than a 20 kPa (3 psi) difference
between the lowest and highest pressure drop, then the fuel injectors may be the cause of the driveability symptom. See the example tables below
to determine if cleaning is appropriate.
6.
If there is a 20 kPa (3 psi) difference, or less, between the highest and lowest fuel pressure drop, the fuel injectors are operating properly and
further diagnostics should be performed on the vehicle.
Example One
Maximum Difference: 68-41 = 27 kPa (10-6 = 4 psi)
Although the pressure drop is greater than 20 kPa (3 psi), cylinder 2 stands out as being rich when compared to the other injectors. Do not clean the
injectors. Replace injector number 2. Charge time to labor operation J5650.
Example Two
Maximum Difference: 48-23 = 25 kPa (7-3 = 4 psi) The pressure drop is greater than 20 kPa (3 psi). Injectors 1 and 3 appear to be lean when compared
to injectors 2, 4, 5 and 6. Clean and re-test pressure drop. If cleaning does not restore flow on injectors 1 or 3, replace the defective injector or injectors
as necessary. Charge time to labor operation J5650.
