Engine Coolant Temperature Sensor; Ignition Timing Procedure; Intake Air Temperature Sensor; Manifold Absolute Pressure (Map) Sensor Test - Chrysler 1998 Voyager Service Manual

NS
DIAGNOSIS AND TESTING (Continued)
either the crankshaft position sensor/camshaft posi-
tion sensor 8 volt supply circuit, or the camshaft
position sensor output or ground circuits. Use the
DRB scan tool to test the camshaft position sensor
and the sensor circuits. Refer to the appropriate Pow-
ertrain Diagnostics Procedure Manual. Refer to the
wiring diagrams section for circuit information.

IGNITION TIMING PROCEDURE

The engines for this vehicle, use a fixed ignition
system. The PCM regulates ignition timing. Basic
ignition timing is not adjustable.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
TEST
Refer to Group 14, Fuel System for Diagnosis and
Testing.
CAMSHAFT POSITION SENSOR AND CRANKSHAFT
POSITION SENSOR
The output voltage of a properly operating cam-
shaft position sensor or crankshaft position sensor
switches from high (5.0 volts) to low (0.3 volts). By
connecting an Moper Diagonostic System (MDS) and
engine analyzer to the vehicle, technicians can view
the square wave pattern.

ENGINE COOLANT TEMPERATURE SENSOR

Refer to Group 14, Fuel System for Diagnosis and
Testing.

INTAKE AIR TEMPERATURE SENSOR

Refer to Group 14, Fuel System, for Diagnosis and
Testing.

SPARK PLUG CONDITION

NORMAL OPERATING CONDITIONS
The few deposits present will be probably light tan
or slightly gray in color with most grades of commer-
cial gasoline (Fig. 23). There will not be evidence of
electrode burning. Gap growth will not average more
than approximately 0.025 mm (.001 in) per 1600 km
(1000 miles) of operation for non platinum spark
plugs. Non-platnium spark plugs that have normal
wear can usually be cleaned, have the electrodes filed
and regapped, and then reinstalled.
CAUTION: Never attempt to file the electrodes or
use a wire brush for cleaning platinum spark plugs.
This would damage the platinum pads which would
shorten spark plug life.
Some fuel refiners in several areas of the United
States have introduced a manganese additive (MMT)
for unleaded fuel. During combustion, fuel with MMT
may coat the entire tip of the spark plug with a rust
Fig. 23 Normal Operation and Cold (Carbon) Fouling
colored deposit. The rust color deposits can be misdi-
agnosed as being caused by coolant in the combustion
chamber. Spark plug performance is not affected by
MMT deposits.
COLD FOULING (CARBON FOULING)
Cold fouling is sometimes referred to as carbon
fouling because the deposits that cause cold fouling
are basically carbon (Fig. 23). A dry, black deposit on
one or two plugs in a set may be caused by sticking
valves or misfire conditions. Cold (carbon) fouling of
the entire set may be caused by a clogged air cleaner.
Cold fouling is normal after short operating peri-
ods. The spark plugs do not reach a high enough
operating temperature during short operating peri-
ods. Replace carbon fouled plugs with new
spark plugs.
FUEL FOULING
A spark plug that is coated with excessive wet fuel
is called fuel fouled. This condition is normally
observed during hard start periods. Clean fuel
fouled spark plugs with compressed air and
reinstall them in the engine.
OIL FOULING
A spark plug that is coated with excessive wet oil
is oil fouled. In older engines, wet fouling can be
caused by worn rings or excessive cylinder wear.
Break-in fouling of new engines may occur before
normal oil control is achieved. Replace oil fouled
spark plugs with new ones.
OIL OR ASH ENCRUSTED
If one or more plugs are oil or ash encrusted, eval-
uate the engine for the cause of oil entering the com-
bustion chambers (Fig. 24). Sometimes fuel additives
can cause ash encrustation on an entire set of spark
IGNITION SYSTEM 8D - 11