Fuel Injector Balance Test

The injector balance test is used to pulse the injector for a precise amount of time, spraying a measured amount of fuel in the intake manifold. As each injector is pulsed, a drop in fuel rail pressure occurs. This pressure drop can be recorded and compared to other injectors. An injector with a pressure drop of 1.5 psi (.11 kg/cm² ) or more, greater than or less than other injectors, should be considered faulty.

NOTE: Allow engine to cool down to avoid irregular readings due to "hot soak" fuel boiling. To prevent flooding, the FUEL INJECTOR BALANCE TEST should not be performed more than once without starting and running engine.

CAUTION: To avoid possible vehicle fire, wrap a shop towel around fitting to absorb fuel spillage.

Ensure engine is at normal operating temperature. Connect Fuel Pressure Gauge (J-34730-1) to pressure test port. Energize fuel pump using fuel pump test connector or Tech 1 scan tool.
Bleed air from fuel gauge and hose to ensure accurate gauge reading. Repeat this procedure until all air is bled from system. Run fuel pump and note fuel pressure. Fuel pressure should be as specified. See FUEL PRESSURE RANGE CHART . If fuel pressure range is not as specified, see BASIC FUEL SYSTEM CHECKS in the BASIC TESTING article.
Turn fuel pump off. When fuel pump stops, pressure may slightly drop then should hold steady. If fuel pressure does not hold steady, refer to BASIC FUEL SYSTEM CHECKS in the BASIC TESTING article.
Install Fuel Injector Tester (J-39021) to an injector. Set amperage supply selector switch to BALANCE TEST, 0.5-2.5 AMP position. Cycle fuel pump on and off to pressurize fuel system. Record stabilized fuel pressure.
Depress PUSH TO START TEST button on fuel injector tester to energize injector. Note fuel pressure the instant fuel gauge needle stops. Record fuel pressure reading. Perform the same test to all injectors.
To obtain pressure drop values, subtract second pressure reading from first pressure reading on each injector. Add all pressure drop values and divide by number of injectors to obtain an average pressure drop.
Retest an injector that appears faulty. Replace any injector with a 1.5 psi (.11 kg/cm² ) difference, either greater than or less than the average pressure drop. If injectors are all okay, remove test equipment, plug in disconnected harness connectors and review SYMPTOMS in the TESTS W/O CODES article.

FUEL PRESSURE RANGE CHART

Application	psi (kg/cm² )
1.9L	38-44 (2.7-3.1)