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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 140 (Engine Controls - System & Component Testing) >> Fuel System (Bi-Fuel & CNG) >> Fuel Injector Coil Test (Bi-Fuel & CNG) >> Diagnostic Procedure

Diagnostic Procedure

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  1. Perform Alternative Fuels Diagnostic System Check - Engine Controls. See ALTERNATIVE FUELS DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing Alternative Fuels Diagnostic System Check - Engine Controls, go to next step.
  2. Observe Engine Coolant Temperature (ECT) with scan tool. Is ECT value within 50-90°F (10-32°C)? If yes, go to next step. If no, go to step  4.
    3. NOTE: Calibrate DMM and test leads to zero ohms in order to prevent misdiagnosis.
  3. Measure resistance of each CNG fuel injector with a DMM. Do any fuel injectors display a resistance outside 1-2 ohms? If yes, go to step  6. If no, go to DIAGNOSTIC AIDS .
  4. Measure resistance of each CNG fuel injector with DMM. Record each fuel injector value. Subtract lowest resistance value from highest resistance value. Is difference equal to, or less than 0.5 ohms? If yes, go to DIAGNOSTIC AIDS . If no, go to next step.
  5. Add all CNG fuel injector resistance values together to obtain a total resistance value. Divide total resistance value by number of fuel injectors to obtain an average resistance value. Subtract lowest and highest individual fuel injector resistance values from average resistance value. Replace CNG fuel injector that displays greatest resistance difference, above or below the average. After repairs, go to step  7.
  6. Replace fuel injector or fuel injectors that are out of specified range. After repairs, go to next step.
  7. Operate system in order to verify repair. Did you correct the condition? If yes, system is okay. If no, go to step  2.
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