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Home >> GMC >> 1991 >> Forward Control 5.7 K, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Testing >> A-3, No-Start Diagnosis >> Engine Controls - Basic Testing >> Fuel System (TBI)
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Fuel System (TBI)

  1. Before checking fuel system for a no-start condition, check ignition for adequate spark. Check for proper fuel pump pressure (9-13 psi) and capacity (one pint in 30 seconds). See A-7, BASIC FUEL SYSTEM CHECKS (GASOLINE).
  2. Crank engine, and watch for injector spray. If injector spray occurs, go to step 5). If no spray occurs, disconnect injector harness, and check for battery voltage at harness.Battery voltage should be present on one injector terminal.If battery voltage is not present, check for blown injector power fuse. If battery voltage is present on both terminals, check for wires shorted to one another.
  3. If battery voltage is present on only one terminal, connect injector test light (also called a "node" light) to injector harness. Crank engine, and note light. If light flashes, check for stored ECM codes. See DIAGNOSTIC CIRCUIT CHECK. If no codes are present, refer to HARD START symptom in TESTS W/O CODES article in this section. If light does not flash, momentarily touch test light from battery voltage to ECM RPM reference terminal (circuit No. 430).
  4. Each time test light is removed from ECM RPM reference terminal, injector test light should flash. If test light does not flash, check for open in RPM reference wire or injector drive (ground) circuit. If wiring is okay, replace faulty ECM. Prior to replacing ECM, check ECM power and ground circuits.
  5. If injector spray occurred while cranking engine, disconnect injector harness,and crank engine.If injector spray or leakage occurs, a no-start condition could be caused by excessive fuel being delivered during cranking. Repair faulty injector or injector seal. If no spray or leakage occurs, refer to HARD START symptom in article TESTS W/O CODES in this section.
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