Lisle 20580 in Line Spark Tester W/Coil On Plug Wire

This compact handheld tester connects between a spark plug and its wire to display a clear, mirror-image flash of the ignition spark while the engine runs. Designed for professional mechanics and DIYers, the tool combines a double-ended short wire (straight and 90° boots) with an additional 7" extension to reach recessed coil-on-plug applications. It’s a simple, visual way to confirm whether a spark is present without removing plugs or using bulky equipment.

How does the Lisle 20580 show if a spark is firing?

When installed inline between the plug and wire, the tester’s transparent window flashes each time the ignition fires, producing a visible mirror-image of the spark. This allows you to confirm spark presence and timing visually while the engine runs.

• Inline installation between plug and wire for live testing
• Transparent window displays spark flashes as they occur
• Works with most ignition systems for on‑the‑spot verification

Will this tester reach recessed or coil-on-plug applications?

Yes — the Lisle 20580 includes a 7" extension plug wire specifically for coil-on-plug units and other recessed plugs. The extension gives extra reach so you can test plugs that are hard to access without disassembly.

• 7" extension plug wire for deeper access
• Double-ended short wire offers straight and 90° boot options
• Fits many modern engines with tight spark plug locations

Is the tool safe and easy to use during engine operation?

Designed for hands-on troubleshooting, the tester lets you observe sparks with the engine running while maintaining a secure connection to the plug/wire. Use basic safety precautions and keep clear of moving parts and hot components.

• Connects inline; no need to remove spark plug for observation
• Visual indication reduces guesswork in ignition diagnostics
• Compact, lightweight design suited for bench or roadside checks

What types of ignition issues can this tool help identify?

The tester helps isolate ignition-related faults by confirming whether a spark is present at each plug location. It’s useful for narrowing down misfires, weak spark, wiring problems, and coil failures as part of a systematic diagnosis.

• Detects absent or intermittent sparks at individual cylinders
• Useful for diagnosing wiring, coil, and connector issues
• Complements compression and fuel-system checks for full troubleshooting

Who is this for: The Lisle 20580 is aimed at professional technicians, home mechanics, and automotive enthusiasts who need a fast, visible way to check spark delivery without complex test equipment. It’s ideal when you need a quick on‑engine confirmation of ignition activity, particularly on engines with recessed plugs or coil‑on‑plug arrangements. Keep it in a tool roll or shop bench for routine troubleshooting, maintenance checks, and rapid in-field diagnostics.