My 12-volt negative ground Ignitor won’t start/runs poorly. What should I check?

If your Ignitor-equipped engine is not starting or is running poorly, follow these troubleshooting steps:

1. Check Grounds
   

   • Measure resistance from the aluminum Ignitor plate to the battery’s negative terminal using a digital multimeter.
     

   • Net resistance should be less than 0.2 ohms.
     

   • If resistance is higher, trace the ground path (Ignitor plate → distributor housing → engine block → battery negative) and correct any poor connections.
     

2. Verify Coil Resistance
   

   • Ensure your coil’s primary resistance matches the requirements for your cylinder count:
     

     • 1 - 6 cylinders: 3.0–4.5 ohms
       

     • 8 & 12 cylinders: 1.5–3.5 ohms
       

   • Include ballast resistor resistance if used.
     

3. Perform a Loaded Voltage Test
   

   • With ignition “ON,” you should see at least 8.0V at the coil positive terminal (11.5V is typical).
     

   • During cranking, voltage should be 8.0V or higher (9.5V is typical). Low voltage may indicate poor wiring, bad connections, or a weak battery/starter.
     

4. Other Common Issues
   

   • Use suppression-type spark plug wires (including coil wire).
     

   • Never leave the ignition on without the engine running - this can damage the Ignitor and coil.
     

   • Ensure the tachometer isn’t grounding the coil’s negative terminal during testing.
     

   • Try a known-good coil to rule out coil failure.
     

   • Inspect the Ignitor for overheating signs (wrinkled or burnt label).
     

5. Bench Testing the Ignitor
   

   • If the above checks don’t resolve the issue, you can remove the Ignitor and perform a bench test per the instructions. A failed Ignitor will show constant battery voltage on the meter without dropping when a magnet passes the module.
     

By following these steps, you can identify whether the issue lies in the Ignitor, the coil, wiring, or another part of the ignition system.