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re: Re: Checking Plug Wires
Many of the automotive tool trucks (Snap On, Mac Tools, etc) and the automotive parts stores
sell a modified spark plug designed to verify if the ignition coil has enough output to fire the plugs
under severe conditions.
It sometimes has a ST-125 part number.
The modified spark plug has no outer electrode and has a alligator clip to connect it to the engine
ground. The plug gap between the center electrode and the outer threads is very large and the
idea is if the spark will jump across this wide gap you have enough reserve coil output to fire
the plugs. I have run across some coils that prevented a car from starting that had a spark
output that "looked" ok but would fail this test with the modified plug.