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Home >> Buick >> 1992 >> LeSabre Custom >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Controls - Basic Testing >> No Start Diagnosis (A-3) >> No Start - Engine Cranks OK (3.1L & 3.4L PFI W/Dis) >> Ignition System ("W" Body)

Ignition System ("W" Body)

  1. Disconnect tachometer wire if equipped. A shorted tachometer or tachometer circuit will prevent vehicle from starting.
  2. Install "Scan" tester. Check for stored ECM trouble codes. Scan TPS voltage. If TPS reading is greater than 2.5 volts, use Code 21 chart first. Scan RPM while cranking engine. If RPM is displayed on "Scan" tester, go to step 5). If RPM is not displayed, check for spark on 2 wires (2-4 or 4-6) using Spark Tester (ST-125). Check one wire at a time. Leave other wires connected to plugs while cranking. If spark occurs on both wires, go to next step. If no spark occurs on either wire, go to step 9). If spark occurs on one wire only, go to step 4).
  3. Turn ignition off. Disconnect 6-wire ignition module connector. Turn ignition on. Monitor scanned RPM while momentarily touching RPM reference circuit wire (circuit No. 430) of ignition module harness connector with a test light connected to battery voltage. If RPM is indicated on "Scan" tester, problem is faulty ignition module-to-harness connection or faulty DIS ignition module. If RPM is not indicated, problem is open or short to ground in RPM reference circuit or faulty ECM.
  4. If spark occurs on one wire only, check pair of wires for plug that did not spark. Each wire should measure less than 30,000 ohms resistance. If wires are okay, switch coil assemblies. If problem moves with coil, replace faulty coil. If problem does not follow coil, ignition module is faulty.
  5. Scan fuel pump signal (PPSW) during cranking. If voltage is not indicated, see Code 54 chart in appropriate G - TESTS W/ CODES article in this section. If voltage is indicated, check for spark on 2 wires (2-4 or 4-6) using Spark Tester (ST-125). Check one wire at a time. Leave other wires connected to plugs while cranking. If spark occurs on both wires, go to next step. If spark does not occur on either wire, ignition module is faulty. If spark occurs on one wire, go to step 4).
  6. If spark occurs on both wires, disconnect No. 1 and No. 6 injector harness connectors. Turn ignition on. With test light connected to ground, probe Pink/Black wires of injector harness connectors. See Fig 1. If light is not on, repair open in injector power supply wire. If test light is on, connect test light to battery voltage. While cranking engine, probe Light Blue wire of injector harness connector. If test light does not flash, go to next step. If test light does flash, recheck fuel system pressure. If fuel pressure is within specification, fuel injection system is okay. See appropriate HARD START symptom in TESTS W/O CODES article in this section.
  7. If test light connected to injector harness connector does not flash (no light), go to next step. If test light connected to injector harness connector is on steady, check injector drive circuit for short to ground. If circuit is not shorted to ground, ensure injector resistance is 12-12.4 ohms. Replace any injector that does not measure correct resistance. If injectors are okay, ECM is faulty.
  8. Check for open or short to battery voltage in injector drive circuit between ECM and injector harness connector. If no problem exists in injector drive circuit, problem is faulty ECM.
  9. If no spark is present and RPM is not indicated on "Scan" tester as determined in step 2), turn ignition off. Disconnect 2-wire connector at ignition module. Turn ignition on. Connect test light across harness connector terminals. If test light is on, go to step 11). If test light is off, probe terminal "B" of harness connector using test light connected to ground.
  10. If test light is off, repair open in ignition module power feed circuit. If test light is on, repair open in ignition module ground circuit wire between terminal "A" and engine ground.
  11. Disconnect crankshaft sensor 3-wire connector at ignition module. Using ohmmeter, check resistance between Purple and Yellow wires of 3-wire harness connector. If resistance is 900-1200 ohms, go to next step. If resistance is less than 900 ohms, crankshaft sensor leads are shorted together or crankshaft sensor is faulty. If resistance is greater than 1200 ohms, repair open in Purple or Yellow wire between harness connector and crankshaft sensor, or replace faulty crankshaft sensor.
  12. Set voltmeter on 2-volt AC position. Crank engine with voltmeter leads connected between Purple and Yellow wires of crankshaft sensor harness. If voltmeter reading is not greater than .1 volt, problem is faulty connection at crankshaft sensor or faulty sensor. If voltmeter reading is greater than .1 volt, replace DIS ignition module.
Fig 1: 3.1L & 3.4L PFI Ignition System Cutlass Supreme, Grand Prix, Lumina & Regal)
G92F04661Courtesy of GENERAL MOTORS CORP.
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