Amazon Has a Spark Plug Tester on Sale for $30

The Ancel Spark Plug Tester is 35% off at Amazon, but the sale ends soon. Put your car’s spark plugs to the test by ordering ...
JSTOR Daily

Plug Fouling Investigations on a Running Engine - An Application of a Novel Multi-Purpose Diagnostic System Based on the Spark Plug

SAE Transactions, Vol. 100, Section 4: JOURNAL OF FUELS & LUBRICANTS (1991), pp. 681-686 (6 pages) A method for non-intrusive measurement of spark plug fouling, burn quality, pre-ignition and spark ...