Hi, no it's not for clamping on, it's for detecting for a spark and so you just touch it on the ht lead

does it work on small engine 4-cycle, 12V

Our Service dept use this all the time on small engines. You do have to properly adjust the dial on the unit for small engines. We use as a quick test.

does this actually detect if the plug wire is pulled loose from the plug itself?

Probably not, but a good visual inspection should. I use it to narrow down suspect cylinders that have a misfire such as a defective coil or wire. I have also found plugs that arc inside the plug boots.

Will this work on fuel injectors ?

No- Just ignitions. Fuel injectors are low voltage.

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66331 Tru-Spark Ignition Firing LED Indicator, Adjustable Sensitivity, Green,Red

66331 Tru-Spark Ignition Firing LED Indicator, Adjustable Sensitivity, Green,Red

Product ID: 7531859

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Details

Brand
Calterm
Power Source
Battery
Style
Adjustable
Color
Green Red
Item dimensions L x W x H
2.2 x 5.9 x

💡Dual LED indicators (Green & Red)

🎚️Adjustable sensitivity dial

🛡️Rugged ABS housing

Description

⚡ Ignite your diagnostics with precision and confidence!

BUILT TO ENDURE - Durable high-impact ABS casing resists oil and withstands tough shop environments.
COMPACT LIGHTWEIGHT - Slim 2.2 x 5.9 x 1.4 inch design weighing just 0.63 oz fits perfectly in your toolkit.
INSTANT VISUAL FEEDBACK - Green LED confirms tester readiness; Red LED flashes with every ignition pulse for real-time monitoring.
UNIVERSAL COMPATIBILITY - Seamlessly works with both DIS and conventional ignition systems—one tool for every pro.
PRECISION SENSITIVITY CONTROL - Exclusive dial isolates plug wires, eliminating false signals for flawless diagnostics.

The Calterm 66331 Tru-Spark Ignition Firing LED Indicator features an exclusive adjustable sensitivity dial to isolate specific plug wires and prevent false signals. Equipped with green and red LEDs for clear operational and ignition pulse feedback, it’s housed in a rugged, oil-resistant ABS casing. Compatible with both DIS and conventional ignition systems, this compact, battery-powered tester is engineered for professional-grade reliability in demanding shop conditions.

Specifications

Brand	Calterm
Power Source	Battery Powered
Style	Adjustable
Color	Green,Red
Item dimensions L x W x H	2.2 x 5.9 x 1.4 inches
UPC	971473127474 046494020230 521227771189 956257381846
Manufacturer	Calterm
Global Trade Identification Number	00046494020230
Model	66331
Item Weight	0.634 ounces
Product Dimensions	2.2 x 5.9 x 1.4 inches
Item model number	66331
Is Discontinued By Manufacturer	No
Manufacturer Part Number	66331