Vehicles equipped with a manual transmis-
sion, a floor mounted shifter, and NO LEVER
below the ignition key: The ignition key cylinder
must be depressed to allow it to be rotated into the
LOCK or ACCESSORY position. If it is difficult to
rotate the key to the LOCK or ACCESSORY position,
the lock mechanism within the steering column may
be defective. This mechanism is not serviceable. If
repair is necessary, the steering column assembly
must be replaced. Refer to Group 19, Steering for
procedures.
DIAGNOSIS AND TESTING
SPARK PLUG CONDITIONS
NORMAL OPERATING
The few deposits present on the spark plug will
probably be light tan or slightly gray in color. This is
evident with most grades of commercial gasoline
(Fig. 14). There will not be evidence of electrode
burning. Gap growth will not average more than
approximately 0.025 mm (.001 in) per 3200 km (2000
miles) of operation. Spark plugs that have normal
wear can usually be cleaned, have the electrodes
filed, have the gap set and then be installed.
Some fuel refiners in several areas of the United
States have introduced a manganese additive (MMT)
for unleaded fuel. During combustion, fuel with MMT
causes the entire tip of the spark plug to be coated
with a rust colored deposit. This rust color can be
misdiagnosed as being caused by coolant in the com-
bustion chamber. Spark plug performance may be
affected by MMT deposits.
COLD FOULING/CARBON FOULING
Cold fouling is sometimes referred to as carbon
fouling. The deposits that cause cold fouling are basi-
cally carbon (Fig. 14). A dry, black deposit on one or
two plugs in a set may be caused by sticking valves
or defective spark plug cables. Cold (carbon) fouling
of the entire set of spark plugs may be caused by a
clogged air cleaner element or repeated short operat-
ing times (short trips).
WET FOULING OR GAS FOULING
A spark plug coated with excessive wet fuel or oil
is wet fouled. In older engines, worn piston rings,
leaking valve guide seals or excessive cylinder wear
can cause wet fouling. In new or recently overhauled
engines, wet fouling may occur before break-in (nor-
mal oil control) is achieved. This condition can usu-
ally be resolved by cleaning and reinstalling the
fouled plugs.
OIL OR ASH ENCRUSTED
If one or more spark plugs are oil or oil ash
encrusted (Fig. 15), evaluate engine condition for the
cause of oil entry into that particular combustion
chamber.
ELECTRODE GAP BRIDGING
Electrode gap bridging may be traced to loose
deposits in the combustion chamber. These deposits
accumulate on the spark plugs during continuous
stop-and-go driving. When the engine is suddenly
subjected to a high torque load, deposits partially liq-
uefy and bridge the gap between electrodes (Fig. 16).
Fig. 14 Normal Operation and Cold (Carbon) Fouling
1 – NORMAL
2 – DRY BLACK DEPOSITS
3 – COLD (CARBON) FOULING
Fig. 15 Oil or Ash Encrusted
8D - 8
IGNITION SYSTEM
WJ
DESCRIPTION AND OPERATION (Continued)