Ignition Systems

Spark Plug Parts

Removing a Spark Plug

Special sockets with a rubber boot inside the end allows you to fit the socket over top of the spark plug without chipping the ceramic sides of the plug.

This also helps you line up the socket properly.

NOTE these are always six point sockets!

Setting the Spark Plug Gap

The gap setting is different for each vehicle but most are somewhere between 0.028" and .060". You may have to research the recommended setting for the engine you're working on.

What gives the spark plug its electrical impulse??

The magneto will create a voltage every time the permanent magnet on the flywheel passes by it.

This voltage is sent to the spark plug and the electrons jump (spark) between the centre electrode and the side electrode of the spark plug

Measuring the air gap between flywheel magnet and coil

Rotate the engine flywheel magnets away from the magnetic ignition coil. This allows the coil to be slid backwards and adjusted properly.
Loosen the 1/4-inch magnetic coil mounting bolts with a socket wrench. Slide the magnetic coil backwards by hand. Tighten one of the coil mounting bolts temporarily to hold the magnetic coil in place.
Insert a nonmagnetic feeler gauge tool between the magnetic coil and flywheel to measure the correct coil to the flywheel air gap. The air gap adjusts and sets the correct ignition timing on magnetic coil type engines for proper engine operation. The feeler gauge tool thickness is generally between .006 and .010-inches or between .010 and .014-inches.
Rotate the flywheel so that the flywheel magnets line up directly with the magnetic coil and filler gauge tool.
Loosen the magnetic coil mounting bolt and slide the magnetic coil against the filler gauge tool and flywheel. The flywheel magnets will generally pull the coil to the flywheel, holding the coil in place.
Tighten the magnetic coil mounting bolts with a socket wrench. Rotate the flywheel until the feeler gauge tool slips free from the magnetic coil and flywheel.

How to test an ignition coil

What type of engines do NOT need a spark?

The glow plug in a diesel engine will ignite the diesel fuel/air mixture BUT this only happens becasue the compression stroke increases the temperature and pressure of the diesel/air mixture to the point where it self ignites.

This is called the "Autoignition Temperature"

The Autoignition temperature of gasoline is 280 degrees Cesius

The Autoigniton temperature of diesel is 210 degrees Celsius.

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