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Home >> Buick >> 1989 >> Reatta >> Repair and Diagnosis >> Engine Performance >> System >> 3.3L/3.8L Component Tests >> Description >> Chart C2A - Injector Balance Test

Chart C2A - Injector Balance Test

NOTE: If it is determined that injectors are dirty, they should be cleaned using approved injector cleaning procedures prior to performing this test. Complete CHART A7 - FUEL SYSTEM DIAGNOSIS before starting this 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 that has a pressure drop difference of 1.5 psi (.11 kg/cm2 ) or more, greater 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. In order to prevent flooding, the INJECTOR BALANCE TEST should not be repeated more than once, without starting and running engine.
CAUTION: To reduce risk of vehicle fire, when installing or removing fuel gauge, use a shop towel wrapped around fitting to avoid fuel spillage.
NOTE: Test numbers refer to test numbers on diagnostic charts.
  1. With ignition off, connect Fuel Pressure Gauge (J-34730-1) to pressure tap. Unplug harness connector at all injectors. Connect Injector Tester (J-34730-3) to one of the injectors.
  2. Follow manufacturer's instructions for use of the adapter harness. Ignition should be turned off for at least 10 seconds to complete ECM shutdown cycle.
  3. Turn ignition on. Fuel pump should run at least 2 seconds after ignition is turned on. Bleed air from gauge and hose to ensure accurate gauge reading. Repeat this procedure until all air is bled from system. Turn ignition off for at least 10 seconds.
  4. Turn ignition on again to bring fuel pressure to maximum. Record initial pressure reading. Energize tester one time and note pressure drop at lowest point.
  5. Disregard any slight pressure drop after low point is reached. Subtracting second pressure reading from initial reading indicates amount of injector pressure drop.
  6. Repeat test step 4) on each injector and compare amount of pressure drop. Recheck injectors that do not read within pressure drop range. Replace injector(s) that fail second check.
  7. If injectors are all okay, plug in harness connectors and review SYMPTOMS in TROUBLE SHOOTING section.
Fig 1: Chart C2A, Injector Balance Test
G111192
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