Kohler CV680 Ignition Coil (Resistance Test)
A resistance check can screen a Kohler CV680 ignition module, but it cannot prove the module works under operating conditions. Confirm the engine’s full model and specification first, use the matching service manual for test points and limits, then verify spark with an approved tester. Check both cylinders, and rule out wiring and kill-circuit faults before replacing parts.
A sound diagnosis can protect the resale value of a mower or other machine with a CV680. Replacing a good ignition module adds cost without fixing the fault; leaving an intermittent no-start problem unresolved can make the equipment harder to sell. I start with the engine’s identity and basic checks, then use resistance readings as clues rather than verdicts.
CV680 Identification, Isolation & Safety Preparation
The CV680 is a 674 cc (41.1 cu in), two-cylinder, four-cycle Kohler Command PRO engine with electronic magneto ignition. Each cylinder has its own ignition module. Before testing or ordering parts, find the engine’s full model, specification, and serial numbers; procedures and parts can vary by specification.
Confirm the engine and prepare safely
The engine identification label supplies information needed to find the right service instructions and parts. Use the specification number, not just “CV680,” when looking up resistance limits or module procedures. A manual for a different CV680 specification may describe different parts or test points.
Park on level ground, disengage the PTO, set the brake, stop the engine, remove the key, and let hot parts cool. Disconnect the battery’s negative lead before inspecting wiring or isolating a module. Keep fuel away from sparks and open flames.
This engine is four-cycle. It does not use premixed fuel or two-cycle oil. If the machine has a no-start problem, check that the fuel and oil are appropriate for the machine and follow its manual.
Inspect before measuring
A multimeter measures electrical resistance, or how much a component opposes current through a test path. On an ignition module, however, internal electronics can make a simple resistance reading hard to interpret. Inspect the plug, cap, module wiring, connectors, grounds, and kill-wire insulation for damage, looseness, corrosion, or rubbing first.
Check each cylinder separately. A damaged plug or loose connection can mimic a failed module. Look around the flywheel area for visible damage, but do not remove parts or adjust clearances unless the service procedure calls for it.
| Check | What to look for | What it may indicate |
|---|---|---|
| Spark plug and cap | Cracks, fouling, loose fit, damaged insulation | A plug or cap fault can interrupt spark |
| Module connectors | Corrosion, loose fit, damaged pins | Poor electrical contact |
| Kill wire | Chafing or insulation worn through | It may ground the ignition and stop spark |
| Ground points | Loose or corroded connections | A poor ground can disrupt operation |
| Flywheel area | Visible damage or debris | Further inspection may be needed |
Next step: identify the exact engine specification, then use its manual to decide which resistance test applies.
Ignition-Coil Resistance and Spark-Test Procedure
Resistance testing is a screening step, not a stand-alone pass-or-fail test. Use the CV680 service procedure for the exact module, meter connections, and limits. If resistance is outside that specification, investigate further; if it appears normal, still confirm ignition with a spark tester while cranking.
Isolate the module and take readings
Disconnect the module’s kill wire and any other connections only as directed by the service manual. A grounded kill circuit can suppress spark even when the module itself is serviceable. Never leave the kill circuit disconnected after diagnosis, and do not run the engine with safety or stop circuits defeated.
Set a digital multimeter to the resistance range specified by the procedure. Place the leads only on the terminals or points named in the manual. Record the reading for each cylinder and compare it with the correct specification. If measuring low resistance, note the meter-lead resistance as the manual directs.
Do not use a generic internet value as a CV680 pass/fail limit. Meter range, lead polarity, connection points, and the module’s internal electronics can affect what the meter shows. An open, short, or unstable reading is a reason to continue diagnosis. Treat it as proof of failure only when it violates the applicable Kohler specification.
| Resistance result | What it means | Sensible next step |
|---|---|---|
| Within the correct manual limit | The module passed that resistance check | Continue to a spark test |
| Outside the correct manual limit | The reading does not meet that procedure’s limit | Recheck setup, then follow the manual’s diagnosis |
| Open, shorted, or unstable | The reading needs investigation | Verify lead placement and connections; do not condemn on a generic value |
| No specification found for the module | There is no valid pass/fail comparison | Do not guess; use the correct manual or a qualified service source |
Confirm spark on both cylinders
A spark tester checks whether the ignition system can produce spark while the engine is cranked. Use an approved inline or adjustable tester and follow the CV680 manual for tester gap and procedure. Test both cylinders. Do not hold a spark plug or high-tension lead by hand, and do not crank with exposed leads.
If spark is absent, check the kill circuit, grounds, plug, flywheel key and magnet condition, and cranking speed before replacing a module. A resistance reading cannot show every fault that appears only during cranking or under operating conditions.
| Spark-test result | Likely direction for diagnosis |
|---|---|
| Spark on both cylinders | Continue diagnosis elsewhere if the engine still will not start |
| Spark on one cylinder only | Compare that cylinder’s plug, wiring, module, and connections with the other side |
| No spark on either cylinder | Inspect shared stop wiring, grounds, and test setup before condemning both modules |
| Spark changes as wiring is moved | Inspect for a loose connector or damaged insulation |
A diagnostic pattern from the field
I use a one-cylinder-versus-the-other comparison to keep the diagnosis focused. For example, if one side has spark and the other does not, I first compare the two plugs, caps, connectors, and kill-wire routing. I then follow the manual’s isolation and resistance steps, and finish with the spark tester. This is a diagnostic approach, not proof that a particular part has failed.
If both cylinders lack spark, I give extra attention to shared wiring and test conditions. A kill wire that is grounded or chafed can stop ignition and make a good module look faulty. Isolate that circuit only for the prescribed check, then restore it before the machine returns to service.
Key point: a resistance result narrows the search; the spark test checks actual ignition output.
Wiring, Air-Gap & Ignition-System Maintenance
The ignition-module air gap is the distance between the module and the flywheel. A common Kohler Command setting is 0.20–0.30 mm (0.008–0.012 in), but the exact CV680 specification and service procedure must take priority. Do not adjust the gap based only on a general figure.
Check the air gap and plug gap
If the manual calls for an air-gap check, use its method and measuring tool. A setting that is too wide or too narrow can affect ignition performance. Keep the flywheel and module surfaces clean, and follow the specified tightening steps; do not force the module or assume the common Command setting applies to every specification.
For the applicable CV680 configuration, the spark-plug gap is 0.76 mm (0.030 in). Verify that value against the engine-specification manual before setting or replacing a plug. A correct plug gap does not prove the coil is good, but it removes one basic variable from the test.
| Measurement | Reference value | How to use it |
|---|---|---|
| Spark-plug gap | 0.76 mm (0.030 in) | Verify for the exact engine specification |
| Ignition-module air gap | Common Command setting: 0.20–0.30 mm (0.008–0.012 in) | Confirm in the CV680-specific procedure |
| Coil resistance | No universal pass/fail value stated here | Use only the exact manual’s test points and limits |
Trace wiring faults before replacing parts
Follow the kill wire from the module toward the stop switch and connectors. Look for insulation worn through where the harness touches a frame edge or moving part. Check connectors for secure fit and signs of corrosion. Repair or replace damaged wiring by the machine and engine instructions; do not bypass a stop switch as a permanent fix.
The kill circuit is designed to stop ignition when activated. A short to ground can imitate a bad coil, so test it as directed and restore all connections afterward. If resistance readings and spark results do not agree, recheck the test setup and wiring before buying a module.
Reassembly, Storage & Seasonal Service
Reassembly means returning every tested connection and safety circuit to its proper state before the engine is used. After testing, reconnect the module wiring and kill wire as specified, restore the battery negative lead, and confirm connectors and leads are secure. Do not return the machine to service with a disconnected stop circuit.
Finish the test and prepare for storage
Before starting, confirm that tools and test leads are clear of moving parts. Use the machine’s normal starting procedure, and check for leaks or unusual sounds. If the engine still has a fault, record which cylinder was tested, the resistance readings, the manual specification used, and each spark-test result. Those notes help avoid repeating steps or replacing a part without evidence.
For seasonal storage, follow the equipment and engine manuals. Keep the ignition wiring dry and protected from abrasion, and inspect it before the next start. If the machine fails to start after storage, return to identification, inspection, and testing rather than assuming the coil has failed.
Common diagnostic mistakes
Several shortcuts can lead to a wrong diagnosis or an unsafe repair:
- Applying a resistance value from a different engine or module.
- Measuring through connected wiring when the manual requires an isolated module.
- Replacing a module before checking the kill wire, plug, and ground.
- Testing only one cylinder when both need diagnosis.
- Leaving the kill circuit disconnected after a test.
- Holding a plug or lead by hand while cranking.
Conclusion: Match the test to the engine specification, treat resistance as a screening measurement, and confirm spark with an approved tester. If results remain unclear, take the recorded readings and engine numbers to a Kohler service source or qualified technician.
FAQ: CV680 Ignition-Module Testing
These short answers cover the key decisions in a CV680 ignition diagnosis. The exact engine specification and its service manual control the test limits and procedure; a generic resistance number cannot replace them.
Can I tell if a CV680 ignition coil is bad with an ohmmeter?
Not reliably on resistance alone. Use the correct manual’s test points and limits, then verify spark with an approved tester.
What resistance should a CV680 ignition coil have?
There is no universal value to apply across all CV680 modules. Use the specification for the exact engine and module.
Should I test both cylinders?
Yes. Each cylinder has its own ignition module, so test both sides using the specified procedure.
Can a bad kill wire cause no spark?
Yes. A grounded or chafed kill wire can suppress spark and make a serviceable module appear faulty.
Can I run the engine with the kill wire disconnected?
No. Isolate the wire only for the prescribed test, then reconnect it before operating the machine.
What is the CV680 spark-plug gap?
For the applicable configuration, it is 0.76 mm (0.030 in). Confirm the value in the manual for your engine specification.
What air gap should I set at the ignition module?
A common Kohler Command setting is 0.20–0.30 mm (0.008–0.012 in), but verify the CV680-specific procedure before adjustment.
Does the CV680 use two-cycle fuel mix?
No. It is a four-cycle engine and does not use premixed fuel or two-cycle oil.
What should I check if resistance looks normal but there is no spark?
Check the kill circuit, grounds, plug, flywheel key and magnet condition, and cranking speed. Then repeat the spark test as directed.
Is it safe to test spark by holding the plug?
No. Use an approved inline or adjustable spark tester and follow the manual’s procedure.
(This article was written by one of our staff writers, Harrison Croft. Visit our Meet the Team page.)
