Fuel Injector Balance Test

Injector Balance Test Example:

Circuit Description

The Fuel Injector Balance Test compares the performance of each of the cylinder by using the PCM to shut off fuel injection. The J 39021 Fuel Injector Tester is being used to energize the fuel injector for a precise time period. This measures the performance of each cylinder by the amount of RPM drop caused by that cylinder not producing a power stroke. If proper fuel delivery has been determined, then a cylinder that does not show good performance (RPM drop) indicates either an ignition or mechanical problem.

Diagnostic Aids

Any fuel injector that significantly (more than 10 kPa) requires service.

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 gauge. Place the towel in an approved container when the connection of the fuel pressure gauge is complete.

2. The engine coolant temperature affects the ability of the fuel injector tester to detect a faulty fuel injector. If the engine coolant temperature is NOT between 10°C and 35°C (50°F and 95°F), go to Fuel Inj Coil Test - ECT Outside 10-35 Degrees C. Component Tests and General Diagnostics
3. The first second of the voltage displayed by the DMM may be inaccurate due to the initial current surge, therefore, record the lowest voltage displayed by the DMM after the first second of the test. The voltage displayed by the DMM should be within the specified range. The voltage displayed by the DMM may increase throughout the test as the fuel injector windings warm and the resistance of the fuel injector windings changes. An erratic voltage reading (large fluctuations in voltage that do not stabilize) indicates an intermittent connection within the fuel injector.