Chevrolet CHEVY VAN G10 SERIES Service Manual page 235

ENG INE ELEC TR IC A L 6Y-24
SPARK PLUG AND WIRE SERVICE
Removal and Inspection
1. To disconnect wires, pull only on the b o o t. Pulling on
the wire might cause separation o f th e core o f the wire.
Rem ove spark plugs and gaskets using a 5 /8 " deep socket
on the 5 /8 " hex tap ered plugs. Use care in this operation
to avoid cracking spark plug insulators.
2. Carefully inspect th e insulator and electrodes o f all spark
plugs. Replace any spark plug w hich has a cracked or
b roken insulator. I f the insulator is worn aw ay around
the center electrode, or th e electrodes are burned or
w orn, the spark plug is w orn o u t and should be dis­
carded. Spark plugs w hich are in good condition except
for carbon or oxide deposits should be thoroughly
cleaned and adjusted.
3. The spark plug wires are a special resistance ty p e. The
core is carbon-im pregnated linen. This wire is designed to
elim inate radio and television interference radiation, b u t
is also superior in resistance to cross fire. The resistance
ty pe wire, how ever, is m ore easily dam aged th a n copper
core wire. For this reason care m ust be tak en th a t the
spark plug wires are rem oved b y pulling on th e spark plug
b o ots rather than on the wire insulation. Also, w hen it is
necessary to replace a spark plug b o o t, th e old b oot
should be carefully cu t from th e wire and a small am ount
o f silicone lu bricant used to aid in installing the new
b o o t. If th e wire is stretched, th e core may be b roken
w ith n o evidence o f damage on the ou ter insulation. The
term inal m ay also pull o ff th e wire. I f the core is broken,
it will cause missing. In th e case o f wire damage, it is
necessary to replace the com plete wire assembly as a
satisfactory repair cannot be m ade.
4. Wipe ignition wires w ith cloth m oistened w ith kerosene,
and wipe dry. Carefully bend wires to check for b rittle,
cracked, or loose insulation. Defective insulation will
perm it missing or cross-firing o f engine, therefore defec­
tive wires should be replaced.
5. If the wires are in good condition, clean any term inals
th a t are corroded and replace any term inals th a t are
broken or distorted. Replace any b rok en or deteriorated
cable nipples or spark plug boots.
Spark Plug Cleaning
Spark plugs w hich have carbon or oxide deposits should be
cleaned in a blast type spark plug cleaner. Scraping w ith a
p oin ted tool will not properly remove the deposits and may
damage th e insulator. I f spark plugs have a wet or oily deposit
dip them in a degreasing solvent and then dry thoroughly w ith
dry com pressed air. Oily plugs will cause the cleaning com ­
pound to pack in the shell. Carefully follow the instructions of
th e m anufacturer o f the cleaner being used, cleaning each plug
u n til the interior o f shell and th e entire insulator are clean;
how ever, avoid excessive blasting.
Fig. 1 2i—Setting Spark Plug Gap
Exam ine interior o f plug in good light. Remove any
cleaning com pound w ith com pressed air. If traces o f carbon
oxide rem ain in plug, finish the cleaning w ith a light blasting
o peration. Clean firing surfaces o f center and side electrodes
w ith several strokes o f a fine file.
When spark plugs have been thoroughly cleaned, carefully
inspect for cracks or o th er defects which m ay n o t have been
visible before cleaning.
Adjusting Spark Plug Gap
Use ro u n d wire feeler gages to check the gap betw een spark
plug electrodes o f used plugs (Fig. 12i). Flat feeler gages will
n ot give a correct m easurem ent if the electrodes are worn.
A djust gap by bending the side electrodes only; bending the
center electrode will crack the insulator. A djust gaps to
specification. Setting spark plug gap to o th er th an specifica­
tio n to effect changes
recom m ended.
Installation of Spark Plugs
When installing spark plugs, m ake sure th a t all surfaces on
plugs and in cylinder heads are clean. When installing the 5 /8 "
hex tapered seat spark plugs, tighten to 15 lb. ft., using a 5 /8 "
deep socket, and a torque w rench.
Installation of Spark Plug Wires
No. 1 spark plug wire is installed in the first distributor cap
tow er after the adjusting w indow , moving in the direction o f
8
ro tatio n (V- ), or in the forem ost tow er (L-
are then installed in a clockwise direction according to the
firing order (Figs. lOi and 1 li).
in engine perform ance is
6
). The other wires
C H E V Y V A N SHOP M A N U A L
not