Spark Plug Condition - Chipped Electrode Insulator; Spark Plug Condition - Pre-Ignition Damage - Jeep 1987 Wrangler Workshop Manual

ENGINES
ENGINE TUNE-UP PROCEDURES
Spark Plug Condition - Chipped Electrode Insulator
A chipped electrode insulator usually results
from bending the center electrode while
adjusting the spark plug electrode gap.
P L U G S WITH THIS CONDITION
MUST B E R E P L A C E D .
60770C
Under certain conditions, severe detonation can
also separate the insulator from the center
electrode.
Spark Plug Condition - Pre-ignition Damage
60770D
The Insulators appear relatively clean of
deposits.
Determine if the spark plug has the correct heat
r a n g e r a t i n g , if the ignition timing is
overadvanced or if other conditions are causing
engine overheating.
N O T E : The heat range rating refers to the
operating temperature of a particular type spark
plug. Spark plugs are designed to operate within
specific temperature ranges depending upon
the thickness and length of the center electrode
porcelain insulator.
Pre-ignition damage is caused by excessive
engine temperature. First the center electrode
liquefies, and somewhat later, the ground (side)
electrode.
PLUGS WITH THIS
CONDITION MUST B E R E P L A C E D .
B-24