How to Tell if a Cub Cadet Ignition Coil Is Bad
The ignition coil creates the voltage needed to fire the spark plug. When an ignition coil begins to fail, a Cub Cadet mower may become difficult to start, lose power, stall after warming up, or produce no spark at all.
Common Symptoms of a Bad Ignition Coil
- The engine cranks but does not start
- There is no visible spark at the spark plug
- The engine runs when cold but stops after warming up
- The mower starts intermittently
- The engine misfires or loses power under load
- One cylinder stops firing on a twin-cylinder engine
These symptoms can also be caused by a bad spark plug, damaged wiring, incorrect coil air gap, or a safety circuit grounding the ignition system.
Inspect the Spark Plug First
Remove the spark plug and look for heavy carbon buildup, cracked porcelain, worn electrodes, or fuel fouling. Replacing or testing the spark plug is usually easier and less expensive than replacing the ignition coil.
Use an inline spark tester to verify whether the ignition system produces a strong, consistent spark while the engine is cranking.
Check the Ignition-Coil Air Gap
The ignition coil must be positioned at the correct distance from the flywheel magnets. If the air gap is too wide, spark output may be weak or absent. If it is too narrow, the coil may contact the flywheel.
Use the engine manufacturer’s specification for the correct air gap. Do not assume that all Cub Cadet engines use the same setting.
Inspect the Kill Wire
The ignition coil typically has a small wire that grounds the coil when the engine is switched off. Damaged wiring, a pinched wire, or a failed safety switch can ground the coil continuously and prevent spark.
Inspect the wire and connector for damaged insulation, corrosion, and contact with the engine or frame.
Heat-Related Ignition Failure
A failing ignition coil may work while cold and stop producing spark after the engine becomes hot. When the engine cools, it may start again. This pattern strongly suggests a heat-sensitive ignition component, although fuel-tank venting and carburetor problems should also be considered.
Twin-Cylinder Engine Diagnosis
On a twin-cylinder engine, one failed coil can allow the mower to continue running on a single cylinder. The engine may sound uneven, lose power, vibrate excessively, or struggle when the blades are engaged.
Compare spark output between both cylinders and inspect both plugs before determining that a coil has failed.
Confirm the Engine Model
Cub Cadet mowers may be equipped with Kohler, Kawasaki, Briggs & Stratton, or other engines. Ignition components must be matched to the engine model and specification number, not only to the mower’s visible model name.
Northline Parts carries selected aftermarket ignition components for Cub Cadet mower applications. Verify the original part number, engine model, and connector arrangement before ordering.