What Is A Kohler Command Ignition System? (Testing & Gap)
A Kohler Command ignition system creates and controls the spark that lights the fuel-air mixture in the engine. It typically includes a spark plug, ignition module, flywheel magnet, and stop circuit. To test it safely, identify the exact engine model and specification first: plug gap, module air gap, and test steps can vary.
An engine can turn over strongly and still have no spark. That can make ignition trouble seem mysterious, but the system is a set of parts that can be checked in order. The important catch is that “Kohler Command” names a range of engines, not one exact ignition setup.
I use the model and specification number as the starting point whenever I explain an ignition test. It helps avoid setting a gap or replacing a part based on a number that belongs to a different engine.
What a Kohler Command ignition system does
A Kohler Command ignition system makes a timed electrical spark at the spark plug so the engine can run. On many models, a magnet on the flywheel works with an ignition module to produce that spark. A stop circuit can ground the module and prevent spark when the engine is switched off.
The ignition system does not supply fuel or turn the engine. It provides the spark that helps ignite the fuel-air mixture inside the cylinder. If the plug, module, wiring, or related parts cannot do their job, the engine may crank without starting.
“Command” covers several engine families and ignition designs. Some use conventional magneto ignition, while others have electronic ignition features and model-specific service steps. Do not assume that a procedure or gap from one Command engine applies to another.
What the main ignition parts do
These parts work together, but each has a different job. Knowing their roles helps you inspect the right area and understand test results. The owner’s manual or Kohler service manual for your exact engine remains the guide for part numbers and specifications.
- Flywheel magnet: As the flywheel rotates, its magnet passes the ignition module and helps create the electrical energy needed for spark.
- Ignition module: Also called an ignition coil in many service discussions, it produces high voltage for the spark plug.
- Spark plug: Its electrodes create a spark inside the cylinder. The plug must be the correct type and have the specified electrode gap.
- Kill wire and stop circuit: The wire connects the ignition system to the engine’s stop controls. Grounding the circuit stops spark. Safety switches may also be part of the equipment’s control system.
- High-tension lead and boot: These carry the module’s high voltage to the spark plug. Cracks, poor connections, or damage can interrupt the path.
Identify the engine and prepare for testing
The model and specification number identify which Kohler Command engine you have. Find the engine ID label and use those details to locate the matching Kohler service information. This matters because the correct spark plug, gaps, torque values, and test procedure may differ by engine.
Before testing, park the equipment on level ground, disengage the PTO, set the brake, and let hot parts cool. Keep hands, clothing, tools, and test leads away from rotating parts. Disable fuel flow where practical, and keep sparks well away from fuel and fuel vapors.
Confirm the ignition type and service instructions before disconnecting wires or adjusting parts. If access requires removing guards, follow the equipment manual and reinstall them before operation. Do not guess at wire connections or fastener torque.
How to test a Kohler Command ignition system
A safe test checks for spark without touching the high-voltage lead or plug. Start with a visual inspection, then use an approved adjustable spark tester. If there is no spark, isolate the stop circuit before deciding that the ignition module has failed.
1. Inspect before testing
With the engine off, check the spark plug, boot, high-tension lead, module mounting, kill-wire insulation and connectors, and visible flywheel area. Look for loose hardware, corrosion, oil, damaged insulation, or a cracked lead. Confirm that the plug matches the engine specification.
If the plug is fouled or oily, do not treat replacement as a complete diagnosis. The contamination may point to another engine condition that needs attention. Use the specified plug gap rather than bending the electrode to an improvised setting.
2. Check for spark with a tester
Connect an approved adjustable spark tester between the plug lead and engine ground, following the tester instructions. Crank the engine and watch the tester. A 1/4-inch (6.4 mm) tester gap is a common screening setup, not a universal Kohler procedure; follow the exact manual if it calls for another method or setting.
Never hold the plug or lead by hand, or press the plug against the engine to look for spark. High voltage can cause injury, and an exposed spark can ignite fuel vapors. Keep the tester and leads clear of moving parts.
3. Isolate the stop circuit if spark is absent
If there is no spark, switch the ignition off before disconnecting the module’s kill lead. Then retest using the approved procedure. If spark returns with the kill lead disconnected, the fault may be in the stop switch, a safety interlock, or wiring that is grounding the circuit.
If spark still does not appear, check the plug, module, module-to-flywheel air gap, flywheel magnet, and flywheel key according to the service manual. A failed module is only one possibility. Replace parts after testing rather than using replacement as the first diagnostic step.
Never leave the kill lead disconnected to make the engine run. A damaged or bypassed stop circuit can prevent the equipment from shutting down as intended. Reconnect the wiring after diagnosis and verify normal stopping.
4. Set the module-to-flywheel air gap
The air gap is the clearance between the ignition module and flywheel. A common range for some Command engines is 0.008–0.012 inch (0.20–0.30 mm), but the exact value and adjustment method depend on the model. Use the Kohler manual, not the range alone, as your setting.
If adjustment is permitted by the manual, use the specified setup method or a nonmagnetic feeler gauge. Tighten the module fasteners to the model-specific torque. Do not substitute a generic torque value, and keep the gap even as directed by the service procedure.
Common gaps and what they mean
Three different “gaps” may come up during ignition service. They measure different things and are not interchangeable: the plug gap is at the electrodes, the module air gap is beside the flywheel, and the tester gap is used to screen spark strength.
| Measurement | Common reference | What it measures | Important limit |
|---|---|---|---|
| Spark-plug electrode gap | 0.030 in (0.76 mm) on many models | Space between the plug electrodes | Confirm the engine and plug specification |
| Module-to-flywheel air gap | 0.008–0.012 in (0.20–0.30 mm) is common on some Command engines | Clearance between the module and flywheel | Use the exact manual value and method |
| Spark-tester gap | 1/4 in (6.4 mm) is a common screening setup | Tester setting used while checking for spark | Follow the prescribed test procedure |
These are reference points, not a universal specification sheet. Plug type, plug torque, module-fastener torque, idle speed, and governed high speed are also model-specific. Use the engine manual for each value.
Worked diagnostic examples
The following examples are common diagnostic patterns, not reports about a specific Kohler engine. They show how test results can narrow the search without encouraging guesswork. Actual steps and allowable checks depend on the engine and equipment manuals.
Example: spark returns after the kill lead is isolated
Suppose the engine has no spark with its normal wiring connected, but spark appears after the kill lead is disconnected for the test. That result points toward the stop circuit, such as a grounded wire, switch, or interlock. It does not identify which one, so inspect and test the circuit using the correct diagram.
Reconnect the kill lead after testing. Do not run the engine with the stop circuit disabled, and do not bypass an interlock as a repair.
Example: no spark remains after isolation
If there is still no spark with the kill lead isolated for the test, the stop circuit is less likely to be the cause. Check the plug and lead, then inspect module mounting and the specified air gap. Continue to the flywheel magnet, flywheel key, and module only as the service procedure directs.
A visible spark at the tester does not prove that every part is perfect under all conditions. If the engine still will not start, other systems may also need diagnosis.
After testing and routine care
Before returning the equipment to service, switch it off, remove the tester, reconnect all wiring, and reinstall guards. Confirm that the engine starts and stops using its normal controls. If the stop control does not work, do not operate the equipment until the fault is repaired.
Kohler Command engines are generally four-stroke engines. Use the gasoline and crankcase oil specified for the exact engine; do not premix two-stroke oil into the fuel unless that engine’s documentation explicitly requires it. For storage, follow the engine or equipment manual’s fuel-stabilization or draining instructions, and keep the plug lead and ignition parts protected from moisture and corrosion.
Frequently asked questions
What is a Kohler Command ignition system?
It is the group of parts that creates and controls the spark needed for combustion, including the plug, ignition module, flywheel magnet, and stop circuit.
How do I test a Kohler Command engine for spark?
Use an approved adjustable spark tester between the plug lead and engine ground. Crank the engine and follow the test procedure for its exact model.
What spark-tester gap should I use?
A 1/4-inch (6.4 mm) tester gap is a common screening setup. It is not universal, so use the manual’s specified tester gap or procedure when provided.
What is the correct Kohler Command coil air gap?
Some Command specifications fall around 0.008–0.012 inch (0.20–0.30 mm), but the correct clearance depends on the model. Check the exact service manual.
What is the spark-plug gap on a Kohler Command engine?
A 0.030-inch (0.76 mm) gap is common on many models. Confirm the engine specification and plug listing before setting it.
Why does my engine have no spark?
Possible causes include a faulty plug, damaged lead, grounded kill wire, stop-switch or interlock issue, incorrect module gap, flywheel problem, or failed module. Test in order rather than replacing parts at random.
Can I run the engine with the kill wire disconnected?
No. Disconnecting the lead is only a temporary diagnostic step when the service procedure allows it. Reconnect it and confirm normal shutdown before operating the equipment.
Does a Kohler Command engine use two-stroke fuel mix?
Command engines are generally four-stroke. Use the specified fuel and crankcase oil; do not add two-stroke oil to the fuel unless the exact engine documentation says to do so.
What should I do if spark returns when I disconnect the kill lead?
Inspect the stop switch, safety interlocks, connectors, and wiring for a short or ground fault. Repair the cause and restore the stop circuit. Do not leave it disconnected.
The safest route is simple: identify the exact engine, follow its service data, and test one part of the ignition path at a time. When a result points to wiring or a safety control, repair that circuit rather than bypassing it.
(This article was written by one of our staff writers, Evan Bradley. Visit our Meet the Team page.)
