Honda GX390 No Spark

The Honda GX390 engine is a reliable and efficient workhorse commonly found in a variety of equipment such as generators, pressure washers, and lawn mowers. However, as with any engine, you may occasionally encounter a no-spark issue. In this article, we will discuss the possible causes of a no-spark issue in your Honda GX390 engine and provide troubleshooting tips and solutions to help you get your engine up and running again.

  1. Check the Spark Plug: The first thing to examine when facing a no-spark issue is the spark plug. A damaged, fouled, or improperly gapped spark plug can prevent the engine from starting. To inspect the spark plug, remove it from the engine and look for any damage, carbon deposits, or an improper gap. Clean the spark plug or replace it if necessary, making sure to properly gap the new spark plug according to the manufacturer’s specifications.
  2. Inspect the Ignition Coil: The ignition coil is responsible for generating the high voltage necessary to create a spark. If the ignition coil is faulty, it may not produce the required voltage, leading to a no-spark condition. Check the ignition coil for physical damage and ensure that it is securely mounted. You can also use a multimeter to test the coil’s primary and secondary windings for continuity. If the readings are out of the specified range, replace the ignition coil.
  3. Test the Kill Switch : The kill switch is designed to shut off the engine in case of an emergency. If the kill switch is malfunctioning or stuck in the “off” position, it may prevent the engine from starting. Check the kill switch for proper operation and ensure that it is not shorted or stuck in the closed position. If the switch is faulty, replace it.
  4. Examine the Flywheel: The flywheel plays a crucial role in the ignition process by providing the necessary magnetic field for the ignition coil to generate a spark. Inspect the flywheel for any signs of damage, such as cracked or broken magnets or a damaged key. Ensure that the flywheel is properly seated on the crankshaft and that the keyway is intact. If you find any issues with the flywheel, replace it as necessary.
  5. Check the Wiring and Connections: A loose or damaged wire can interrupt the flow of electricity, causing a no-spark issue. Carefully inspect the wiring and connections throughout the ignition system, including the spark plug wire, ignition coil, and kill switch. Repair or replace any damaged or corroded wires and ensure all connections are clean and tight.
  6. Inspect the Ignition Timing: Incorrect ignition timing can also lead to a no-spark condition. Check the timing marks on the flywheel and the ignition coil, ensuring they are properly aligned. If the timing is off, adjust the ignition coil position or replace the flywheel key as necessary.
  7. Test the CDI (Capacitor Discharge Ignition) Module: The CDI module is responsible for controlling the ignition timing and the strength of the spark. A faulty CDI module can cause a no-spark issue. Use a multimeter to test the CDI module according to the manufacturer’s specifications. If the module is found to be faulty, replace it.
  8. Inspect the Ignition Pulse Generator: The ignition pulse generator is responsible for sending a signal to the CDI module, indicating when to release the stored energy to create a spark. A malfunctioning pulse generator may prevent the engine from sparking. To test the ignition pulse generator, use a multimeter to measure its resistance, comparing the results to the manufacturer’s specifications. If the resistance is out of range, consider replacing the ignition pulse generator.
  9. Check the Grounding: Proper grounding is essential for the ignition system to function correctly. Inspect the engine’s grounding points, ensuring they are clean and free from corrosion. Tighten or clean any loose or dirty connections to ensure proper grounding.
  10. Verify the Valve Timing: Incorrect valve timing can affect the engine’s ability to generate a spark. Inspect the timing belt or chain, as well as the camshaft and crankshaft gears, to ensure proper alignment. Refer to the manufacturer’s specifications and service manual for the correct timing marks and alignment procedure. If necessary, adjust the valve timing or replace any damaged components.
  11. Assess the Compression: Adequate compression is necessary for the engine to produce a spark. Perform a compression test using a compression tester to determine if there is sufficient compression in the engine. If the compression is low, it may indicate a problem with the piston rings, cylinder head, or valves. In this case, further engine inspection and repair may be required.

Possible Causes for No Spark in Honda GX390

CauseSymptomsTesting ProcedureSolutionCost of Repair
Faulty Spark PlugEngine cranks but doesn’t startCheck spark plug resistanceReplace spark plug$5 – $10
Faulty Ignition CoilNo spark, engine won’t startCheck ignition coil resistanceReplace ignition coil$50 – $100
Dirty or Faulty Spark ArrestorNo spark, engine won’t startCheck spark arrestor for blockageClean or replace spark arrestor$10 – $20
Faulty Flywheel KeyNo spark, engine won’t startRemove flywheel and check key for damageReplace flywheel key$5 – $10
Faulty Ignition SwitchNo spark, engine won’t startCheck ignition switch for continuityReplace ignition switch$10 – $20

Testing Procedures for No Spark in Honda GX390

ComponentSymptomsTesting ProcedureResultSolution
Spark PlugEngine cranks but doesn’t startRemove spark plug and check for spark when cranking engine with plug grounded to engine block.Spark presentMove to next component
Ignition CoilNo spark, engine won’t startCheck resistance of primary and secondary winding of ignition coil using an ohmmeter.Resistance in rangeMove to next component
Spark ArrestorNo spark, engine won’t startRemove spark arrestor and inspect for blockage or damage. Clean or replace as necessary.Clean or replaceMove to next component
Flywheel KeyNo spark, engine won’t startRemove flywheel and inspect flywheel key for damage or wear. Replace if necessary.Key intact and secureMove to next component
Ignition SwitchNo spark, engine won’t startCheck continuity of ignition switch using a multimeter.Continuity presentMove to next component

Symptoms of No Spark in Honda GX390

SymptomPossible Cause
Engine cranks but doesn’t startFaulty spark plug
Engine doesn’t crank and no sparkFaulty ignition coil
Engine runs rough or stalls at high RPMsDirty or faulty spark arrestor
Engine won’t start but cranksFaulty flywheel key
Engine won’t start and doesn’t crank or sparkFaulty ignition switch

Honda GX390 Ignition Coil Resistance Values

ComponentResistance Value
Primary Winding0.4 – 0.5 ohms
Secondary Winding5,000 – 10,000 ohms

Honda GX390 Spark Plug Specifications

Spark Plug TypeNGK BPR5ES
Spark Plug Gap0.028 – 0.031 inch
Spark Plug Torque14 – 15 lb-ft
Spark Plug Resistance5,000 – 10,000 oh



A no-spark issue in your Honda GX390 engine can be frustrating, but with a systematic approach, you can identify and fix the problem. By following these troubleshooting tips and solutions, you can quickly restore your engine’s performance and get your equipment back in working order. Remember to always follow safety precautions and consult your engine’s service manual for specific details and procedures.


  • Ray Barnes

    Ray Barnes, our Senior Staff Writer and a Golf Analyst with a PhD in Sports Analytics, is a beacon of insight in the golfing world. With a deep understanding of the sport's nuances, statistical analysis, and a talent for demystifying complexities, he provides in-depth analysis and captivating narratives that engage golf enthusiasts worldwide.

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