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HOMESERVICE MANUALSBUICK1990REGAL CUSTOM, 3.8 L, 4T60/ME9REPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - BASIC TESTINGNO START DIAGNOSISNO START - ENGINE CRANKS OKAY (PFI WITH C(3)I)IGNITION SYSTEM (3.3L)
1990 Buick Regal Custom, 3.8 L, 4T60/ME9

Ignition System (3.3L)

1990 Buick Regal Custom, 3.8 L, 4T60/ME9SECTION Ignition System (3.3L)
  1. Disconnect tachometer wire (if equipped). A shorted tachometer will not allow vehicle to start. Check for adequate spark with Spark Tester (ST-125). Check for spark on plug wires No. 1, 3 and 5 (one at a time). Leave matching plug wire connected while checking for spark. If spark jumped tester on all plug wires, check fuel system. If spark did not occur on any plug wire, go to step 4). If spark did not jump tester on all plug wires, verify plug wire resistance is less than 30,000 ohms. Replace as necessary. If wires are okay, go to next step.
  2. If spark jumped tester on one, but not all plug wires, remove 2 fasteners holding effected coil assembly. Remove coil from module. Connect a test light to 2 exposed terminals on the module. Crank engine. If test light flashes, check for poor coil to module connections. If connections are okay, replace faulty coil.
  3. If test light does not flash, replace ignition module. Also, check primary coil resistance (.5-.9 ohm). Replace coil if necessary.
  4. Turn ignition off. Disconnect ignition module connector. Turn ignition on. Check for battery voltage on terminal "M" of ignition module harness. See Figure and Figure . Repair open or short, or replace ignition fuse as necessary. If battery voltage is present, turn ignition off and disconnect fuel pump relay. Install injector test light in injector harness connector. Connect test light to battery voltage and repeatedly touch to terminal "C" of the ignition module harness connector.
  5. Injector test light should flash each time test light is touched to terminal "C". If injector test light flashes, go to step 7). If not, backprobe ECM injector drive terminals (BC11 and BC12) with a test light to ground. If light is off, check for loss of power to fuel injector harness or open between injectors and drive terminals. If test light is on, disconnect ALL injectors. With test light connected to ground, check for voltage on both terminals of each injector harness.
  6. If voltage is present on both wires of any or all injectors, check for short to voltage on injector drive circuit. If battery voltage is present on only one wire of each injector harness, check for open or shorted circuit No. 430 (RPM reference high), poor connections at ECM terminals BC11 and BC12 or a faulty ECM.
  7. Turn ignition off and reconnect ignition module connector. Disconnect dual crank (combination) sensor. Turn ignition on. Using a DVOM, measure voltage between sensor harness terminals "C" and "D." If 10-12 volts are not present, check for poor connections at ignition module, open or short in combination sensor harness or replace faulty ignition module.
  8. If 10-12 volts are present at combination sensor connector, turn ignition off. Disconnect No. 6 spark plug wire from coil tower. NEVER crank engine with a spark plug wire off coil. Damage to coil or ignition module may occur. Attach Spark Tester (ST-125) to coil tower. Install injector test light in any injector harness.
  9. Turn ignition on. Jumper dual crank sensor connector terminal "A" to terminal "B". Using a test light connected to ground, momentarily touch terminal "A". If injector test light flashes and spark tester sparks, check for poor connections at dual crank sensor. If connections are okay, replace faulty dual crank sensor. Inspect dual crank sensor and pulley for signs of rubbing.
  10. If spark did not occur and injector test light did not flash, check for poor connections at ignition module or replace faulty ignition module.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.