Things You'll Need
Instructions
Disengage the engine cowls and panels to gain full access to the ignition harness.
Remove the ignition leads from each spark plug. Use either a 7/8-inch or 3/4-inch open-end wrench, depending on the spark plugs installed on your aircraft.
Inspect the end of each lead. There should be a metal spring extending out from the center of the lead. The spring is connected to the center conductor of the ignition harness, and makes electrical contact with the spark plug. The harness is defective if the spring is missing.
Inspect the entire length of the ignition harness. Look for damage to the braided outer shielding or cuts into the harness. Pay particular attention to the point where the harness is clamped to the engine.
Connect a high-voltage tester to the under-test harness lead. Connect the wire marked "+12V" on the tester to the aircraft's positive battery terminal. Connect the tester's black high-voltage lead to either the tested harness's shield or the engine ground. Connect the tester's red high-voltage lead to the center conductor of the under-test ignition lead.
Press the "Test" button on the high-voltage tester. An ignition harness lead is good if you observe a continuous spark in the tester's window. If you do not see a spark, release the "Test" button and rotate the propeller one quarter turn. Retest the same harness lead. The absence of a spark in the window a second time indicates a bad ignition harness lead.
Test the other harness ignition leads using a similar procedure. Ensure all leads in both harnesses achieve normal test results.
Reinstall and tighten the spark plug leads on the tested harnesses.
Reinstall the aircraft engine cowl.
Perform the aircraft engine run-up and test.