Fuel Injector Balance Test

Fuel Injector Balance Test:

****This bulletin 61-63-16, Date: February 1997, is being issued to inform technicians of a revision to the Injector Balance Test. This revised procedure will help the technician to use the Injector Balance Test with greater clarity and accuracy.****

Circuit Description
The Fuel Injector Tester J 39021, the Injector Switch Box J 39021-210 and the Injector Harness Connector J 39021-301 energize the injector for a precise amount of time allowing a measured amount of fuel into the manifold. This causes a drop in system fuel pressure that can be recorded and used to compare each injector. All injectors should be within the same pressure drop range, the average pressure drop value for the injectors is ±10 kPa (1.5 psi).

Caution: In order to reduce the risk of fire and personal injury, wrap a shop towel around the fuel pressure connection. 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.

Test Description
4. The engine coolant temperature must be below the operating temperature in order to avoid irregular fuel pressure readings due to Hot Soak fuel boiling.

5. The fuel pressure should be within the specified range. If the fuel pressure is not within the specified range, go to Fuel System Diagnosis. System Diagnosis - Fuel System

6. The fuel pressure should reach a steady value. If the fuel pressure does not reach a steady value, refer to Fuel System Diagnosis. System Diagnosis - Fuel System

7. If the pressure drop value for each fuel injector is within 10 kPa (1.5 psi) of the average pressure drop value, the fuel injectors are flowing properly. Calculate the pressure drop value for each fuel injector by subtracting the second pressure reading from the first pressure reading. Refer to the illustration above.

NOTE: Technicians diagnosing vehicles with misfire DTCs (P0300-P0308) must perform the Injector Coil Test and the Injector Balance Test prior to injector replacement.