Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

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Spark Plug Test







1. Remove the spark plug from the engine and connect it to the spark plug cable boot.
2. Ground the spark plug outer electrode (body), and crank the engine. Check for spark across the electrodes.
3. Remove the spark plug from the boot and visually inspect it for cracks in its insulation.
4. Replace the spark plug if it has a weak spark and/or detective insulation.