Clean, Test And Install Spark Plugs; Ignition System Service And Repairs - Pontiac Grand Prix Service Manual

6C-2 1569
PONTIAC SERVICE MANUAL
valves or, if accompanied by oil consumption, worn
rings or low crank speed. If compression is subnormal,
tune-up will probably not be satisfactory. (See specifi-
cations at end of section 6 for correct compression
pressures.)
NOTE: The compression check is important because an
engine with low or uneven compression cannot be tuned
successfully to give peak performance. Therefore, it is
essential that improper compression be corrected before
proceeding with an engine tune-up.
CLEAN, TEST AND INSTALL SPARK PLUGS
1. Inspect each plug individually for badly worn
electrodes, glazed, broken or blistered porcelains and
replace plugs where necessary. For optimum engine
performance and economy, it is recommended that
spark plugs be replaced every 12000 miles. Refer to
spark plug diagnosis information presented in Engine
Electrical for an analysis of plug conditions.
2. Clean serviceable spark plugs thoroughly, using an
abrasive-type cleaner. File the center electrode flat.
3. Inspect each spark plug for make and heat range.
All plugs must be of the same make and number of
heat range. (See section 6E for correct spark plug
usage.)
4. Adjust spark plug gaps to .035" using a round feeler
gauge.
CAUTION: Never bend the center electrode to adjust
gap. Always adjust by bending ground or side electrode.
5. If available, test plugs with a spark plug tester.
6. Inspect spark plug hole threads and clean before
installing plugs. Corrosion deposits can be removed
with a 14 mm. x 1.25 SAE spark plug tap (available
through local jobbers) or by using a small wire brush
in an electric drill. Use plenty of grease on tap to catch
any chips.
CA UTION: Use extreme care when using tap to prevent
cross threading. Also crank engine several times to blow
out any material dislodged during cleaning operation.
7. Install spark plugs to engine with new gaskets and
tighten to 25 Ib. ft. torque.
Improper installation is one of the greatest single
causes of unsatisfactory spark plug performance.
Improper installation is the result of one or more of
the following practices:
Installation of plugs with insufficient torque to fully
seat the gasket.
Installation of the plugs using excessive torque which
changes gap settings.
Installation of plugs on dirty gasket seal.
Installation of plugs to corroded spark plug hole
threads.
Failure to install plugs properly will cause them to
operate at excessively high temperatures and result in
reduced operating life under mild operation or a m -
plete destruction under severe operation where the
intense heat cannot be dissipated rapidly enough.
Always remove corrosion deposits in hole threads
before installing plugs. When corrosion is present in
threads, normal torque is not sufficient to compress the
plug gasket and early failure from overheating will
result.
Always use a new gasket and wipe seats in head clean.
The gasket must be fully compressed on clean seats to
complete heat transfer and provide a gas tight seal in
the cylinder. For this reason as well as the necessity of
maintaining correct plug gap, the use of correct torque
is extremely important during installation.
IGNITION SYSTEM SERVICE AND REPAIRS
1. Replace brittle or damaged spark plug wires. Install
all wires to proper spark plug. Proper positioning of
spark plug wires in supports is important on V-8
engines to prevent cross-fuing.
2. Tighten all ignition system cone nections.
3. Replace or repair any wires that are frayed, loose or
damaged.
4. Remove distributor cap, clean cap and inspect for
cracks, carbon tracks and burned or corroded ter-
minals. Replace cap where necessary.
5. Clean rotor and inspect for damage or deterioration.
Replace rotor where necessary.
6. Check the distributor centrifugal advance mecha-
nism by turning the distributor rotor as far as possible,
then releasing the rotor to see if the springs return it to
its original osition. If the rotor does not return
readily, the
1
istributor must be disassembled and the
cause of the trouble corrected.
7.
Check to see that the vacuum advance control
operates freely by turning the movable breaker plate
to see if the spring returns to its original position. Any
stiffness in the operation of the spark control will
affect the ignition timing. Correct any interference or
binding condition noted.
8. Examine'distributor points and clean or replace if
necessary.
Contact points with an overall gray color and only
slight roughness or pitting need not be replaced.
Dirty points should be cleaned with a clean point file.