High internal resistance in aviation spark plugs is rapidly becoming a concern that many pilots and mechanics are beginning to recognize as a source of rough running engines and chronic magneto related problems. Realizing that a growing number of maintenance facilities and pilot/owners are incorporating a spark plug resistance check as part of their preventive maintenance, Tempest has introduced its AT5K resistance tester.
Q: I have been noticing an intermittent miss on the left mag during mag checks on the O-235L2C in my 1981 Cessna 152 (about 670 SMOH that included new Lycoming cylinders and pistons). About 30 hours ago when I cleaned, regapped, and rotated the plugs, I found that the lower plug on the #4 cylinder was filled with oil around the inner electrode and ceramic insulator. [Read more…]