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Fuel Injector Balance Test

  1. Ensure engine temperature is less than normal operating temperature. If engine is at normal operating temperature, there may be abnormal pressure readings because of hot-soak fuel vaporization. Removing fuel filler cap may reduce effect of fuel vaporization. Turn ignition off. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELEASE . Install fuel pressure gauge to fuel rail.
  2. Connect fuel injector tester to No. 1 injector. Connect tester Red lead to battery positive terminal and Black lead to battery negative terminal. Activate fuel pump and bleed air from fuel pressure gauge. Turn fuel pump off and allow fuel pressure to stabilize. Record stabilized fuel pressure. Set fuel injector tester for a 500 mS pulse.
  3. Using fuel injector tester, trigger fuel injector No. 1 and record stabilized fuel pressure. Move tester to fuel injector No. 2. Turn fuel pump on and allow fuel pressure to stabilize. Record stabilized fuel pressure. Trigger fuel injector No. 2 and record stabilized fuel pressure. Repeat procedure for remaining fuel injectors, recording fuel pressures before and after triggering each fuel injector. Ensure fuel system is pressurized before triggering each fuel injector.
  4. Compare injector pressure drop for all injectors to the average pressure drop. Injector pressure drop is the difference between recorded pressures before and after fuel injector is triggered. For example, if the pressure before the injector is triggered is 30 psi and after is 16 psi, the injector pressure drop will be 14 psi. Add pressure drop values for all 8 injectors and divide by 8 to obtain the average fuel injector pressure drop.
  5. The pressure drop for each injector should be within 2 psi (more or less than) of the average injector pressure drop. For example, if the average fuel pressure drop is 14 psi, then the injector pressure drop for each injector could be 12-16 psi.
  6. Closely monitor injector pressure drop on each cylinder that has a misfire. If an injector is clogged or restricted, the injector pressure drop will be more than 2 psi greater (i.e.: more than 16 psi) than the average. If the injector is allowing to much fuel or is leaking, the injector pressure drop will be more than 2 psi less (i.e.: less than 12 psi) than the average. Replace any injector with a fuel pressure drop more than 2 psi greater or less than the average pressure drop. If pressure drop for all injectors are within 2 psi of the average, go to FUEL INJECTOR ELECTRICAL CHECK .
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