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HOMESERVICE MANUALSPONTIAC1991GRAND PRIX GT, 3.4 X, AUTOMATICREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - BASIC TESTINGNO START DIAGNOSIS (A3)NO START - ENGINE CRANKS OKAY (PFI WITH C(3)I)IGNITION SYSTEM (3.8L)
1991 Pontiac Grand Prix GT, 3.4 X, Automatic

Ignition System (3.8L)

1991 Pontiac Grand Prix GT, 3.4 X, AutomaticSECTION Ignition System (3.8L)
  1. Disconnect tachometer wire (if equipped). A shorted tachometer or tachometer circuit will not allow the vehicle to start. Disconnect the cam sensor and attempt to start engine. If engine starts, see cam sensor trouble code test procedures in the appropriate TESTS W/CODES article. 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 for cause of no start. If spark did not occur on any plug wire, go to step 4).
  2. If spark did not jump tester on all plug wires, verify that plug wire resistance is less than 30,000 ohms. Replace as necessary. If wires are okay, go to next step. If spark jumped tester on one, but not all plug wires, remove 6 fasteners holding coil assembly. Tilt coil assembly and disconnect coil's control wire from the module.
  3. Connect a test light between the common Blue wire and control wire of affected coil. Crank engine. If test light flashes, check for poor coil to module connections. If connections are okay, replace faulty coil. 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 "P" of ignition module harness. See Fig 1-Fig 4 . 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 terminal "D" of the ignition module harness connector.
    Fig 1: 3.8L PFI Ignition System (Bonneville, Eighty-Eight, Ninety-Eight, LeSabre, Park Avenue, & Touring Sedan)
    G91D07437Courtesy of GENERAL MOTORS CORP.
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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.