LEMON Manuals: Even more car manuals for everyone
Home >> Chevrolet >> 1994 >> Lumina Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Testing >> No Start Diagnosis (A-3) >> No Start - Engine Cranks Okay (3.1L & 3.4L MFI With Dis) >> Ignition System (3.1L VIN T "W" Bodies)

Ignition System (3.1L VIN T "W" Bodies)

  1. Disconnect tachometer wire (if equipped). A shorted tachometer or tachometer circuit will prevent vehicle from starting.
  2. Install scan tester. Check for stored PCM trouble codes. Scan TP sensor voltage. If TP sensor reading is greater than 2.5 volts, use Code 21 chart first. Scan RPM while cranking engine. If RPM signal is displayed on scan tester, go to step 6). If RPM is not displayed, check for spark on 2 wires (2-4 or 4-6) using Spark Tester (ST-125).
  3. Check one wire at a time. Leave other wires connected to plugs while cranking. If spark is present on both wires, go to next step. If no spark is present on either wire, go to step 12). If spark is present on one wire only, go to step 5).
  4. 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. See Fig 1 . If RPM is indicated on scan tester, problem is faulty ignition module-to-harness connection or faulty ignition module. If RPM is not indicated, problem is open or short to ground in RPM reference circuit or faulty PCM.
  5. If spark occurs on one wire only, check pair of wires for plug that did not spark. Ensure each wire measures 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.
  6. Scan fuel pump signal (PPSW) during cranking. If voltage is not indicated, see diagnostic trouble Code 54 in appropriate TESTS W/CODES article in the ENGINE PERFORMANCE section below. If voltage is indicated, install Spark Tester (ST-125). Check for spark on 2 wires (2-4 or 4-6). Check one wire at a time one wire at a time. Leave other wires connected to plugs while cranking. If spark is present on both wires, go to next step. If no spark is present on either wire, go to step 12).
    • G - TESTS W/CODES - 3.1L
    • G - TESTS W/CODES - 3.4L
    • G - TESTS W/CODES - 3.8L
  7. Disconnect injector harness connectors. Probe each connector with test light connected to battery voltage. Crank engine. Test light should flash. If test light flashed, go to next step. If test light did not flash or illuminate, go to step 9). If test light stayed on steady, go to step 11).
  8. Turn ignition off. Check fuel pressure. Fuel pressure should be 32-47 psi (2.2-3.3 kg/cm2 ). If fuel pressure is as specified, refer to HARD START under TESTS W/O CODES article in the ENGINE PERFORMANCE section. If fuel pressure is not as specified, diagnose fuel system.
  9. Turn ignition on. Probe both injector harness terminals with test light connected to ground. If test light illuminated on both terminals, go to next step. If test light illuminated only on one of the terminals, check injector harness. If test light did not illuminate on both terminals, check open in injector power feed circuit No. 439 (Pink/Black wire).
  10. Reconnect injector harness connectors. Turn ignition on. Disconnect PCM connector. Turn ignition on. With test light connected to ground, probe PCM terminals No. BC11 and BC12. Test light should illuminate. If test light illuminates, replace faulty PCM. If test light did not illuminate, check injector harness for open circuit.
  11. Check injector circuit for short to ground or faulty PCM, causing test light to stay on steady. If circuit or PCM is okay, perform injector balance test. See INJECTOR BALANCE TEST under appropriate I - SYS/COMP TESTS article in the ENGINE PERFORMANCE section below.
    • I - SYSTEM/COMPONENT TESTS - 3.1L
    • I - SYSTEM/COMPONENT TESTS - 3.4L
    • I - SYSTEM/COMPONENT TESTS - 3.8L
  12. Disconnect ignition control module connector. Turn ignition on. Connect test light between ignition module terminals. If test light illuminates, go to next step. If test light did not illuminate, move test light from ignition control module terminal "B" to ground. If test light illuminates, repair open in ground circuit. If test light did not illuminate, repair open in ignition feed circuit No. 439 (Pink/Black wire).
  13. Disconnect crankshaft position sensor connector from ignition control module. Check resistance between sensor harness terminals "A" and "C". Resistance should be 900-1200 ohms. If resistance is as specified, go to next step. If resistance is less than 900 ohms, check for shorted sensor leads or faulty crankshaft position sensor. If resistance is greater than 1200 ohms, check for open sensor circuit or faulty crankshaft position sensor.
  14. Set DVOM to 2-volt AC position. Crank engine and observe voltage reading. Reading should be greater than .1 volt. If voltage is as specified, replace ignition control module. If voltage is not as specified, check for faulty connection or faulty crankshaft position sensor.
Fig 1: 3.1L (VIN T) MFI Ignition System (Lumina)
G94C34068Courtesy of GENERAL MOTORS CORP.
scientia non olet · About LEMON Manuals