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Home >> GMC >> 1990 >> Forward Control 3.9 L >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Injectors >> Test Preparation
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Test Preparation

  1. Remove injector nozzles from engine. Clean carbon from tip area of nozzle with soft brass wire brush. DO NOT use steel brush or motorized brush to clean nozzle tip. Damage to nozzle tip may result.
    CAUTION: Use Nozzle Socket (J 36142) to remove and replace injection nozzle. Attach socket to 30mm hex portion of nozzle. Failure to do so will result in damage to the injector nozzle.
  2. Connect injector nozzle to injection nozzle tester. Place clear plastic tubing on both fuel return fittings to prevent bleed-off from being confused with leaks. Close tester shutoff valve to pressure gauge.
  3. Fill tester with test fluid. Fill and flush nozzle assembly with test fluid by operating tester lever briskly and repeatedly. This purges air from injector nozzle and coats all parts with test fluid.
WARNING: When testing injectors, keep spray contained to avoid serious injury. DO NOT allow injector to release line pressure on hands, arms or any part of body. Pressure of atomized test spray has sufficient penetrating power to puncture flesh.
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