Fuel Injector: Testing and Inspection

CIRCUIT DESCRIPTION
The Fuel Injector Balance Test is performed when a misfire, knock, excessive smoke, or rough running condition exists with no electrical diagnostic trouble codes (DTCs). During the test the engine control module (ECM) turns OFF individual injectors while the engine is running and the scan tool displays engine RPM. If a fuel injector is turned OFF and there is a different engine speed change observed on the scan tool when compared to the other cylinders, that cylinder has a fuel injector or engine compression condition. If there is a balance rate of more than 4 cubic mm or less than -4 cubic mm on any of the cylinders, that cylinder has a fuel injector or engine compression condition. If a fuel injector is turned OFF and the engine noise or smoke disappears, that cylinder has a fuel injector or engine compression condition.

TEST DESCRIPTION

Fuel Injector Balance Test with Tech 2 - Steps 1-6:

Fuel Injector Balance Test with Tech 2 - Steps 7-9:

The numbers below refer to the step numbers on the diagnostic table.
3. A balance rate between -4 cubic mm and +4 cubic mm will not cause a driveability concern. A balance rate less than -4 cubic mm, between 4 cubic mm and 14 cubic mm will cause a driveability concern without any DTCs. A balance rate of more than 15 cubic mm will set a DTC.
4. This step determines if the ECM can control a stable fuel pressure. A high balance rate may be caused by a fuel injector or compression only if the ECM can control fuel pressure