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Maintenance
Checking and changing spark plugs
1.
Twist and pull only on the spark plug wire boot (pulling on
wire may cause separation of the core of the wire).
2.
Remove spark plugs using a 5/8-inch spark plug socket or
a 5/8-inch box wrench. Use care to avoid cracking the spark
plug insulators.
3.
Carefully inspect the insulators and electrodes of all spark
plugs.
— Replace any spark plug which has a cracked or bro-
ken insulator or which has loose electrodes.
— If the insulator is worn away around the center elec-
trode, or the electrodes are burned or worn, the spark
plug is worn out and should be discarded.
— Spark plugs that are in good condition, except for car-
bon or oxide deposits, should be thoroughly cleaned
and gapped.
The spark plug wires are a special resistance type. The core is
carbon-impregnated linen. This type wire is superior to copper
core wire in its resistance to crossfire; however, it is more eas-
ily damaged than copper core. For this reason, pull on the
spark plug boots to remove the spark plug wires, rather than
pulling on the wire insulation. If the wire is stretched, the core
may be broken with no evidence of damage on the outer insu-
lation. If the core is broken, it will cause misfiring. In the case of
wire damage, it is necessary to replace the complete wire as-
sembly since a satisfactory repair cannot be made.
4.
Clean ignition wires with a cloth moistened in kerosene,
and wipe dry. Bend wires to check for brittle, cracked or
loose insulation. Defective insulation will permit misfir-
ing, cross-firing, or spark to ground; therefore, defec-
tive wires must be replaced.
5.
If the wires are in good condition, clean any terminals that
are corroded and replace any that are broken or distorted.
Replace any wires with broken or deteriorated cable nipples
or spark plug boots.
6.
Clean spark plugs.
Spark plugs that have carbon or oxide deposits should be
cleaned in a blast type spark plug cleaner. Scraping with a
pointed tool will not properly remove the deposits and may
damage the insulator. If spark plugs have a wet or oily deposit,
dip them in a decreasing solvent and dry thoroughly with com-
pressed air. Oily plugs will cause the cleaning compound to
pack in the shell. Carefully follow the instructions of the manu-
facturer of the cleaner being used. Clean each plug until the
interior of shell and entire insulator is cleaned. Avoid excessive
blasting.
68
7. Examine interior of plug in good light. Remove any clean-
ing compound with compressed air. If traces of carbon or
oxide remain in plug, finish the cleaning with a light blast-
ing operation. Clean firing surfaces of center and side elec-
trodes with several strokes of a fine cut file.
8. When spark plugs have been thoroughly cleaned, care-
fully inspect them for cracks or other defects that may not
have been visible before cleaning.
9.
Use a round wire feeler gauge to check the gap between
the spark plug electrodes. (Flat feeler gauges will not give
a correct measurement if the electrodes are worn.) Adjust
gap by bending the side electrode only. Bending the cen-
ter electrode will crack the insulator. Setting the spark plug
gap to any other specification in an attempt to improve idle
or affect engine performance is not recommended.
10. See the diagrams for correct installation of spark plugs and
wires.
For proper engine performance it is very important that the cor-
rect spark plugs be used. When installing spark plugs, make
sure that the threads in the cylinder
3.0 GS
head and all surfaces on plugs and in
cylinder heads are clean. Tighten spark plugs the specified
amount. All engines use tapered seat plugs without gaskets.
Do not operate engine if spark plug boots or high-tension
leads are torn or cracked. This condition can allow exter-
nal sparks, which could ignite any fuel vapors in the en-
gine compartment.
Spark plug wires must be arranged between the distributor cap
and spark plugs in the order of firing sequence. If spark plug
wires are not correctly installed, misfiring or cross-firing will re-
sult.
The 8.1Gi-B/GXi-A and DPX 375/420 engines use a distribu-
torless ignition system with one coil per cylinder. Refer to the
Specifications section for correct firing order.
7741591 / 2003-12
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