02.10.2022 Views

Automotive Electrical and Electronic Systems Classroom Manual Fifth Edition Update by John F. Kershaw

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

254 Chapter Eleven

Figure 11-56.

A resistor-type spark plug.

Figure 11-58.

A long-reach, short-thread spark plug.

Figure 11-57. A comparison of a standard and an

extended-core spark plug.

Wide-Gap Spark Plugs

The electronic ignition systems on some late-model

engines require spark plug gaps in the 0.045- to

0.080-inch (1.0- to 2.0-mm) range. Plugs for such

systems are made with a wider gap than other plugs.

This wide gap is indicated in the plug part number.

Do not try to open the gap of a narrow-gap plug to

create the wide gap required by such ignitions.

Copper-Core Spark Plugs

Many plug manufacturers are making plugs with

a copper segment inside the center electrode. The

copper provides faster heat transfer from the electrode

to the insulator and then to the cylinder head

and engine coolant. Cooper-core plugs are also

extended-tip plugs. This combination results in a

more stable heat range over a greater range of engine

temperatures and greater resistance to fouling

and misfire.

Platinum-Tip Spark Plugs

Platinum-tip plugs are used in some late-model

engines to increase firing efficiency. The platinum

center electrode increases electrical conductivity,

which helps prevent misfiring with lean

mixtures and high temperatures. Since platinum

is very resistant to corrosion and wear from combustion

chamber gases and heat, recommended

plug life is twice that of other plugs.

Long-Reach, Short-thread Spark Plugs

Some late-model GM engines, Ford 4-cylinder engines,

and Ford 5.0-liter V-8 engines use 14-mm,

tapered-seat plugs with a 3/4-inch reach but have

threads only for a little over half of their length,

Figure 11-58. The plug part number includes a suffix

that indicates the special thread design, although

a fully threaded plug can be substituted if necessary.

Advanced Combustion Igniters

This extended-tip, copper-core, platinum-tipped

spark plug was introduced by GM in 1991. It combines

all the attributes of the individual plug designs

described earlier and uses a nickel-plated shell for

corrosion protection. This combination delivers a

plug life in excess of 100,000 miles (160,000 km).

No longer called a spark plug, the GM advanced

combustion igniter (ACI) has a smooth ceramic insulator

with no cooling ribs. The insulator is coated

with a baked-on boot release compound that prevents

the spark plug wire boot from sticking and

causing wire damage during removal.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!