Figure 15-7. Typical Spark Plug Construction and Heat Range Descriptions
g. Ballast Resistors (Fig. 15-10). A ballast resistor
(3) Some spark plugs Incorporate an auxiliary
(booster) gap In the top terminal. This gap allows the
is used between the ignition switch and the points. It
coil to build a higher voltage and reduce misfiring,
effectively will control primary Ignition voltage to prevent
especially when spark plugs are dirty or fouled. A
premature burning of the points. It contains a resistor
booster gap spark plug is shown In figure 15-9.
element inside of a ceramic casing.
element is made of a special material that increases
Figure 15-8. Resistor Spark Plugs
Figure 15-9. Booster Gap Spark Plugs