Chart A-7 Injector Balance Test

Chart A-7 Injector Balance Test:

Circuit Description:
The Fuel Injector Tester (J39021) is used to energize the injector for a precise amount of time, thus spraying a measured amount of fuel into the manifold. This causes a drop in fuel rail pressure that can be recorded and used to compare each injector. All injectors should have the same pressure drop + 10 kPa (1.5 psi).

Chart Test Description
Number(s) below refer to circled number(s) on the diagnostic chart.

1. An engine cool down period (10 minutes) is necessary to avoid irregular readings due to hot soak fuel boiling. With the ignition "OFF," connect fuel gage J34730-1 or equivalent to fuel pressure tap. Wrap a shop towel around fitting while connecting gage to avoid fuel spillage.

^ Disconnect injector jumper harness connector.

^ Connect J39021-60 to injector jumper harness connector.

^ Disconnect injector harness at injectors 2, 3, and 4. If required, remove MAP and EGR solenoid to gain access to injector 2. (Refer to "On-Vehicle Service," for removal procedures.)

^ Set amperage supply selector switch to the 0.5 - 2.5 amp position for the balance test.

Follow manufacturer's instructions for use of adaptor harness. Ignition must be "OFF" at least 10 seconds to complete PCM shutdown cycle. Fuel pump should run about 2 seconds after the ignition is turned "ON." At this point, insert clear tubing attached to vent valve into a suitable container and bleed air from gage and hose to insure accurate gage operation. Repeat this step until all air is bled from gage.

2. Turn ignition "OFF" for 10 seconds and then "ON" again to get fuel pressure to its maximum. Record this initial pressure reading. Pressure may drop, wait until no movement of needle on gauge is apparent. Energize tester one time and note pressure drop at its lowest point. (Disregard any slight pressure increase after drop hits low point.) Subtract this second pressure reading from the initial pressure reading to calculate the actual amount of injector pressure drop.

3. Disconnect adapter J34730-60 from injector harness connector. Connect adapter J24730-60 to remaining injectors and repeat test on each injector. Compare the amount of drop. Usually, good injectors will have virtually the same drop. Retest any injector that has a pressure difference of 10 kPa, either more than or less than the average of the other injectors on the engine. Replace any injector that also fails the retest. If the pressure drop of all injectors is within 10 kPa (1.5 psi) of this average, the injectors appear to be flowing properly. Reconnect the injector harness and review the "Symptoms."

NOTICE: The entire test should not be repeated more than once without running the engine to prevent flooding. (This includes any retest on faulty injectors.)