ignition DODGE RAM 2001 Service Manual Online

REMOVAL - DIESEL
The camshaft position sensor (CMP) is located
below the fuel injection pump (Fig. 9). It is attached
to the back of the timing gear cover housing.
(1) Disconnect both negative cables from both bat-
teries.
(2) Clean area around CMP.
(3) Disconnect electrical at CMP (Fig. 9).
(4) Remove CMP mounting bolt. Bolt head is
female-hex (Fig. 10).
(5) Remove CMP from engine by twisting and pull-
ing straight back.
(6) Discard CMP o-ring (Fig. 10).
REMOVAL - 3.9L/5.2L/5.9L
The camshaft position sensor is located in the dis-
tributor (Fig. 11).
Distributor removal is not necessary to remove
camshaft position sensor.
(1) Remove air cleaner assembly.
(2) Disconnect negative cable from battery.
(3) Remove distributor cap from distributor (two
screws).
(4) Disconnect camshaft position sensor wiring
harness from main engine wiring harness.
(5) Remove distributor rotor from distributor shaft.(6) Lift the camshaft position sensor assembly
from the distributor housing (Fig. 11).
Fig. 8 CMP Sensor OperationÐ8.0L V-10 Engine
1 - CAM DRIVE GEAR
2 - LOW MACHINED AREA
3 - HIGH MACHINED AREA
4 - CAMSHAFT POSITION SENSOR
5 - AIR GAP
Fig. 9 CMP Location - Diesel
1 - CAMSHAFT POSITION SENSOR (CMP)
2 - BOTTOM OF FUEL INJECTION PUMP
Fig. 10 CMP R/I - Diesel
1 - GEAR HOUSING
2 - O-RING
3 - CMP SENSOR
4 - CMP HEX HEAD BOLT
BR/BEIGNITION CONTROL 8I - 7
CAMSHAFT POSITION SENSOR (Continued)

REMOVAL - 8.0L
The camshaft position sensor is located on the tim-
ing chain case/cover on the left-front side of the
engine (Fig. 12).
A thin plastic rib is molded into the face of the sen-
sor (Fig. 13) to position the depth of sensor to the
upper cam gear (sprocket). This rib can be found on
both the new replacement sensors and sensors that
were originally installed to the engine. The first time
the engine has been operated, part of this rib may be
sheared (ground) off. Depending on parts tolerances,
some of the rib material may still be observed after
removal.Refer to either of the following procedures; Replac-
ing Old Sensor With Original, or Replacing With
New Sensor:
REPLACING OLD SENSOR WITH ORIGINAL
If the original camshaft position sensor is to be
removed and installed, such as when servicing the
timing chain, timing gears or timing chain cover, use
this procedure.
(1) Disconnect the sensor harness connector from
the sensor.
(2) Remove the sensor mounting bolt (Fig. 12).
(3) Carefully pry the sensor from the timing chain
case/cover in a rocking action with two small screw-
drivers.
(4) Remove the sensor from vehicle.
(5) Check condition of sensor o-ring (Fig. 14).
REPLACING WITH NEW SENSOR
If a new replacement camshaft position sensor is to
be installed, use this procedure.
(1) Disconnect the sensor wiring harness connector
from sensor.
(2) Remove the sensor mounting bolt (Fig. 12).
(3) Carefully pry the sensor from the timing chain
case/cover in a rocking action with two small screw-
drivers.
(4) Remove the sensor from vehicle.
INSTALLATION - DIESEL
The camshaft position sensor (CMP) is located
below the fuel injection pump (Fig. 9). It is attached
to the back of the timing gear cover housing.
(1) Install new o-ring to CMP. Apply clean engine
oil to o-ring.
Fig. 11 Camshaft Position SensorÐTypical
1 - SYNC SIGNAL GENERATOR
2 - CAMSHAFT POSITION SENSOR
3 - PULSE RING
4 - DISTRIBUTOR ASSEMBLY
Fig. 12 CMP Location - 8.0L
1 - CAMSHAFT POSITION SENSOR
2 - MOUNTING BOLT
3 - TIMING CHAIN CASE/COVER
Fig. 13 Sensor Depth Positioning RibÐ8.0L V-10
Engine
1 - CAMSHAFT POSITION SENSOR
2 - PAPER SPACER
3 - RIB MATERIAL (FOR SENSOR DEPTH POSITIONING)
8I - 8 IGNITION CONTROLBR/BE
CAMSHAFT POSITION SENSOR (Continued)

(2) Clean area around CMP mounting hole.
(3) To prevent tearing o-ring, install CMP into
gear housing using a twisting action.
(4) Install mounting bolt and tighten to 20 Nm (15
ft. lbs.) torque.
(5) Install electrical connector to CMP.
(6) Connect both negative cables to both batteries.
INSTALLATION - 3.9L/5.2L/5.9L
The camshaft position sensor is located in the dis-
tributor (Fig. 11).
(1) Install camshaft position sensor to distributor.
Align sensor into notch on distributor housing.
(2) Connect wiring harness.
(3) Install rotor.
(4) Install distributor cap. Tighten mounting
screws.
(5) Install air cleaner assembly.
INSTALLATION - 8.0L
If Replacing Old Sensor With Original
The camshaft position sensor is located on the tim-
ing chain case/cover on the left-front side of the
engine (Fig. 12).
When installing a used camshaft position sensor,
the sensor depth must be adjusted to prevent contact
with the camshaft gear (sprocket).
(1) Observe the face of the sensor. If any of the
original rib material remains (Fig. 13), it must be cut
down flush to the face of the sensor with a razor
knife. Remove only enough of the rib material until
the face of the sensor is flat. Do not remove more
material than necessary as damage to sensor may
result. Due to a high magnetic field and possible elec-
trical damage to the sensor, never use an electric
grinder to remove material from sensor.(2) From the parts department, obtain a peel-and-
stick paper spacer (Fig. 13). These special paper
spacers are of a certain thickness and are to be used
as a tool to set sensor depth.
(3) Clean the face of sensor and apply paper
spacer (Fig. 13).
(4) Apply a small amount of engine oil to the sen-
sor o-ring (Fig. 14).
A low and high area are machined into the cam-
shaft drive gear (Fig. 15). The sensor is positioned in
the timing gear cover so that a small air gap (Fig.
15) exists between the face of sensor and the high
machined area of cam gear.
Before the sensor is installed, the cam gear may
have to be rotated. This is to allow the high
machined area on the gear to be directly in front of
the sensor mounting hole opening on the timing gear
cover.
Do not install sensor with gear positioned at
low area (Fig. 16) or (Fig. 15). When the engine
is started, the sensor will be broken.
(5) Using a 1/2 in. wide metal ruler, measure the
distance from the cam gear to the face of the sensor
mounting hole opening on the timing gear cover (Fig.
16).
(6) If the dimension is approximately 1.818 inches,
it is OK to install sensor. Proceed to step Step 9.
Fig. 14 Camshaft Sensor O-RingÐ8.0L
1 - SLOTTED MOUNTING HOLE
2 - SCRIBE LINE
3 - CAMSHAFT POSITION SENSOR O-RING
Fig. 15 Sensor OperationÐ8.0L V-10 Engine
1 - CAM DRIVE GEAR
2 - LOW MACHINED AREA
3 - HIGH MACHINED AREA
4 - CAMSHAFT POSITION SENSOR
5 - AIR GAP
BR/BEIGNITION CONTROL 8I - 9
CAMSHAFT POSITION SENSOR (Continued)

(7) If the dimension is approximately 2.018 inches,
the cam gear will have to be rotated.
(8) Attach a socket to the vibration damper mount-
ing bolt and rotate engine until the 1.818 inch
dimension is attained.
(9) Install the sensor into the timing case/cover
with a slight rocking action until the paper spacer
contacts the camshaft gear. Do not install the sensor
mounting bolt. Do not twist the sensor into position
as damage to the o-ring or tearing of the paper
spacer may result.
(10) Scratch a scribe line into the timing chain
case/cover to indicate depth of sensor (Fig. 14).
(11) Remove the sensor from timing chain case/
cover.
(12) Remove the paper spacer from the sensor.
This step must be followed to prevent the paper
spacer from getting into the engine lubrication sys-
tem.
(13) Again, apply a small amount of engine oil to
sensor o-ring.
(14) Again, install the sensor into the timing case/
cover with a slight rocking action until the sensor is
aligned to scribe line.(15) Install sensor mounting bolt and tighten to 6
N´m (50 in. lbs.) torque.
(16) Connect engine wiring harness to sensor.
Replacing With a New Sensor
(1) Apply a small amount of engine oil to the sen-
sor o-ring (Fig. 14).
A low and high area are machined into the cam-
shaft drive gear (Fig. 15). The sensor is positioned in
the timing gear cover so that a small air gap (Fig.
15) exists between the face of sensor and the high
machined area of cam gear.
Before the sensor is installed, the cam gear may
have to be rotated. This is to allow the high
machined area on the gear to be directly in front of
the sensor mounting hole opening on the timing gear
cover.
Do not install sensor with gear positioned at
low area (Fig. 16) or (Fig. 15). When the engine
is started, the sensor will be broken.
(2) Using a 1/2 in. wide metal ruler, measure the
distance from the cam gear to the face of the sensor
mounting hole opening on the timing gear cover (Fig.
16).
(3) If the dimension is approximately 1.818 inches,
it is OK to install sensor. Proceed to step Step 9.
(4) If the dimension is approximately 2.018 inches,
the cam gear will have to be rotated.
(5) Attach a socket to the vibration damper mount-
ing bolt and rotate engine until the 1.818 inch
dimension is attained.
(6) Install the sensor into the timing case/cover
with a slight rocking action. Do not twist the sensor
into position as damage to the o-ring may result.
Push the sensor all the way into the cover until the
rib material on the sensor (Fig. 13) contacts the cam-
shaft gear.
(7) Install the mounting bolt and tighten to 6 N´m
(50 in. lbs.) torque.
(8) Connect sensor wiring harness to engine har-
ness.
When the engine is started, the rib material will be
sheared off the face of sensor. This will automatically
set sensor air gap.
DISTRIBUTOR
DESCRIPTION
All 3.9L/5.2L/5.9L engines are equipped with a
camshaft driven mechanical distributor (Fig. 17) con-
taining a shaft driven distributor rotor. All distribu-
tors are equipped with an internal camshaft position
(fuel sync) sensor (Fig. 17).
Fig. 16 Sensor Depth Dimensions
1 - 2.01888DO NOT INSTALL SENSOR
2 - SENSOR MOUNTING HOLE OPENING
3 - SENSOR CENTER LINE
4 - TIMING CHAIN COVER
5 - 1.81888OK TO INSTALL SENSOR
6 - CAM DRIVE GEAR
7 - HIGH MACHINED AREA
8 - LOW MACHINED AREA
8I - 10 IGNITION CONTROLBR/BE
CAMSHAFT POSITION SENSOR (Continued)

OPERATION
The camshaft position sensor provides fuel injec-
tion synchronization and cylinder identification.
The distributor does not have built in centrifugal
or vacuum assisted advance. Base ignition timing
and all timing advance is controlled by the Power-
train Control Module (PCM). Because ignition timing
is controlled by the PCM,base ignition timing is
not adjustable.
The distributor is held to the engine in the conven-
tional method using a holddown clamp and bolt.
Although the distributor can be rotated, it will
have no effect on ignition timing.
All distributors contain an internal oil seal that
prevents oil from entering the distributor housing.
The seal is not serviceable.
REMOVAL
CAUTION: Base ignition timing is not adjustable on
any engine. Distributors do not have built in centrif-
ugal or vacuum assisted advance. Base ignition
timing and timing advance are controlled by the
Powertrain Control Module (PCM). Because a con-
ventional timing light can not be used to adjust dis-
tributor position after installation, note position of
distributor before removal.
(1) Remove air cleaner assembly.
(2) Disconnect negative cable from battery.
(3) Remove distributor cap from distributor (two
screws).
(4) Mark the position of distributor housing in
relationship to engine or dash panel. This is done to
aid in installation.(5) Before distributor is removed, the number one
cylinder must be brought to the Top Dead Center
(TDC) firing position.
(6) Attach a socket to the Crankshaft Vibration
Damper mounting bolt.
(7) Slowly rotate engine clockwise, as viewed from
front, until indicating mark on crankshaft vibration
damper is aligned to 0 degree (TDC) mark on timing
chain cover (Fig. 18).
(8) The distributor rotor should now be aligned to
the CYL. NO. 1 alignment mark (stamped) into the
camshaft position sensor (Fig. 19). If not, rotate the
crankshaft through another complete 360 degree
turn. Note the position of the number one cylinder
spark plug cable (on the cap) in relation to rotor.
Rotor should now be aligned to this position.
(9) Disconnect camshaft position sensor wiring
harness from main engine wiring harness.
(10) Remove distributor rotor from distributor
shaft.
(11) Remove distributor holddown clamp bolt and
clamp (Fig. 20). Remove distributor from vehicle.
CAUTION: Do not crank engine with distributor
removed. Distributor/crankshaft relationship will be
lost.
INSTALLATION
If engine has been cranked while distributor is
removed, establish the relationship between distribu-
tor shaft and number one piston position as follows:
Rotate crankshaft in a clockwise direction, as
viewed from front, until number one cylinder piston
is at top of compression stroke (compression should
be felt on finger with number one spark plug
Fig. 17 Distributor and Camshaft Position Sensor
1 - SYNC SIGNAL GENERATOR
2 - CAMSHAFT POSITION SENSOR
3 - PULSE RING
4 - DISTRIBUTOR ASSEMBLY
Fig. 18 Damper-To-Cover Alignment MarksÐTypical
1 - ALIGNMENT MARK
2 - TIMING CHAIN COVER MARKS
3 - CRANKSHAFT VIBRATION DAMPER
BR/BEIGNITION CONTROL 8I - 11
DISTRIBUTOR (Continued)

removed). Then continue to slowly rotate engine
clockwise until indicating mark (Fig. 18) is aligned to
0 degree (TDC) mark on timing chain cover.
(1) Clean top of cylinder block for a good seal
between distributor base and block.
(2) Lightly oil the rubber o-ring seal on the distrib-
utor housing.
(3) Install rotor to distributor shaft.
(4) Position distributor into engine to its original
position. Engage tongue of distributor shaft with slot
in distributor oil pump drive gear. Position rotor to
the number one spark plug cable position.
(5) Install distributor holddown clamp and clamp
bolt. Do not tighten bolt at this time.(6) Rotate the distributor housing until rotor is
aligned to CYL. NO. 1 alignment mark on the cam-
shaft position sensor (Fig. 19) .
(7) Tighten clamp holddown bolt (Fig. 20) to 22.5
N´m (200 in. lbs.) torque.
(8) Connect camshaft position sensor wiring har-
ness to main engine harness.
(9) Install distributor cap. Tighten mounting
screws.
(10) Refer to the following, Checking Distributor
Position.
Checking Distributor Position
To verify correct distributor rotational position, the
DRB scan tool must be used.
WARNING: WHEN PERFORMING THE FOLLOWING
TEST, THE ENGINE WILL BE RUNNING. BE CARE-
FUL NOT TO STAND IN LINE WITH THE FAN
BLADES OR FAN BELT. DO NOT WEAR LOOSE
CLOTHING.
(1) Connect DRB scan tool to data link connector.
The data link connector is located in passenger com-
partment, below and to left of steering column.
(2) Gain access to SET SYNC screen on DRB.
(3) Follow directions on DRB screen and start
engine. Bring to operating temperature (engine must
be in ªclosed loopº mode).
(4) With engine running atidle speed, the words
IN RANGE should appear on screen along with 0É.
This indicates correct distributor position.
(5) If a plus (+) or a minus (-) is displayed next to
degree number, and/or the degree displayed is not
zero, loosen but do not remove distributor holddown
clamp bolt. Rotate distributor until IN RANGE
appears on screen. Continue to rotate distributor
until achieving as close to 0É as possible. After
adjustment, tighten clamp bolt to 22.5 N´m (200 in.
lbs.) torque.
The degree scale on SET SYNC screen of DRB is
referring to fuel synchronization only.It is not
referring to ignition timing.Because of this, do
not attempt to adjust ignition timing using this
method. Rotating distributor will have no effect on
ignition timing. All ignition timing values are con-
trolled by powertrain control module (PCM).
After testing, install air cleaner assembly.
DISTRIBUTOR CAP
DIAGNOSIS AND TESTING - DISTRIBUTOR
CAP
Remove the distributor cap and wipe it clean with
a dry lint free cloth. Visually inspect the cap for
cracks, carbon paths, broken towers or damaged
Fig. 19 Rotor Alignment Mark
1 - CAMSHAFT POSITION SENSOR ALIGNMENT MARK
2 - ROTOR
3 - DISTRIBUTOR
Fig. 20 Distributor Holddown Clamp
1 - CLAMP BOLT
2 - HOLDDOWN CLAMP
3 - DISTRIBUTOR HOUSING
8I - 12 IGNITION CONTROLBR/BE
DISTRIBUTOR (Continued)

rotor button (Fig. 21) or (Fig. 22). Also check for
white deposits on the inside (caused by condensation
entering the cap through cracks). Replace any cap
that displays charred or eroded terminals. The
machined surface of a terminal end (faces toward
rotor) will indicate some evidence of erosion from
normal operation. Examine the terminal ends for evi-
dence of mechanical interference with the rotor tip.DISTRIBUTOR ROTOR
DIAGNOSIS AND TESTING - DISTRIBUTOR
ROTOR
Visually inspect the rotor (Fig. 23) for cracks, evi-
dence of corrosion or the effects of arcing on the
metal tip. Also check for evidence of mechanical
interference with the cap. Some charring is normal
on the end of the metal tip. The silicone-dielectric-
varnish-compound applied to the rotor tip for radio
interference noise suppression, will appear charred.
This is normal.Do not remove the charred com-
pound.Test the spring for insufficient tension.
Replace a rotor that displays any of these adverse
conditions.
IGNITION COIL
DESCRIPTION - 3.9L/5.2L/5.9L
A single ignition coil is used. The coil is not oil
filled. The coil windings are embedded in an epoxy
compound. This provides heat and vibration resis-
tance that allows the coil to be mounted on the
engine.
DESCRIPTION - 8.0L
Two separate coil packs containing a total of five
independent coils are attached to a common mount-
ing bracket. They are located above the right engine
valve cover (Fig. 24). The coil packs are not oil filled.
The front coil pack contains three independent epoxy
Fig. 21 Cap InspectionÐExternalÐTypical
1 - BROKEN TOWER
2 - DISTRIBUTOR CAP
3 - CARBON PATH
4 - CRACK
Fig. 22 Cap InspectionÐInternalÐTypical
1 - CHARRED OR ERODED TERMINALS
2 - WORN OR DAMAGED ROTOR BUTTON
3 - CARBON PATH
Fig. 23 Rotor InspectionÐTypical
1 - INSUFFICIENT SPRING TENSION
2 - CRACKS
3 - EVIDENCE OF PHYSICAL CONTACT WITH CAP
4 - ROTOR TIP CORRODED
BR/BEIGNITION CONTROL 8I - 13
DISTRIBUTOR CAP (Continued)

filled coils. The rear coil pack contains two indepen-
dent epoxy filled coils.
OPERATION - 3.9L/5.2L/5.9L
The Powertrain Control Module (PCM) opens and
closes the ignition coil ground circuit for ignition coil
operation.
Battery voltage is supplied to the ignition coil pos-
itive terminal from the ASD relay. If the PCM does
not see a signal from the crankshaft and camshaft
sensors (indicating the ignition key is ON but the
engine is not running), it will shut down the ASD cir-
cuit.
Base ignition timing is not adjustable on any
engine.By controlling the coil ground circuit, the
PCM is able to set the base timing and adjust the
ignition timing advance. This is done to meet chang-
ing engine operating conditions.
OPERATION - 8.0L
When one of the 5 independent coils discharges, it
fires two paired cylinders at the same time (one cyl-
inder on compression stroke and the other cylinder
on exhaust stroke).
Coil firing is paired together on cylinders:
²Number 5 and 10
²Number 9 and 8
²Number 1 and 6
²Number 7 and 4
²Number 3 and 2
The ignition system is controlled by the Powertrain
Control Module (PCM) on all engines.
Battery voltage is supplied to all of the ignition
coils positive terminals from the ASD relay. If the
PCM does not see a signal from the crankshaft and
camshaft sensors (indicating the ignition key is ONbut the engine is not running), it will shut down the
ASD circuit.
Base ignition timing is not adjustable on the
8.0L V-10 engine.By controlling the coil ground cir-
cuit, the PCM is able to set the base timing and
adjust the ignition timing advance. This is done to
meet changing engine operating conditions.
The PCM adjusts ignition timing based on inputs it
receives from:
²The engine coolant temperature sensor
²The crankshaft position sensor (engine speed)
²The manifold absolute pressure (MAP) sensor
²The throttle position sensor
²Transmission gear selection
REMOVAL - 3.9L/5.2L/5.9L
The ignition coil is an epoxy filled type. If the coil
is replaced, it must be replaced with the same type.
3.9L V-6 or 5.2/5.9L V-8 LDC-Gas Engines: The coil
is mounted to a bracket that is bolted to the front of
the right engine cylinder head (Fig. 25). This bracket
is mounted on top of the automatic belt tensioner
bracket using common bolts.
5.9L V-8 HDC-Gas Engine: The coil is mounted to
a bracket that is bolted to the air injection pump
(AIR pump) mounting bracket (Fig. 26).
(1) Disconnect the primary wiring from the igni-
tion coil.
(2) Disconnect the secondary spark plug cable from
the ignition coil.
Fig. 24 Ignition Coil PacksÐ8.0L V-10 Engine
Fig. 25 Ignition CoilÐ3.9L V-6 or 5.2/5.9L V-8
LDC-Gas Engines
1 - ACCESSORY DRIVE BELT TENSIONER
2 - COIL CONNECTOR
3 - IGNITION COIL
4 - COIL MOUNTING BOLTS
8I - 14 IGNITION CONTROLBR/BE
IGNITION COIL (Continued)

WARNING: 3.9L V-6 OR 5.2/5.9L V-8 LDC-GAS
ENGINES: DO NOT REMOVE THE COIL MOUNTING
BRACKET-TO-CYLINDER HEAD MOUNTING BOLTS.
THE COIL MOUNTING BRACKET IS UNDER ACCES-
SORY DRIVE BELT TENSION. IF THIS BRACKET IS
TO BE REMOVED FOR ANY REASON, ALL BELT
TENSION MUST FIRST BE RELIEVED. REFER TO
THE BELT SECTION OF GROUP 7, COOLING SYS-
TEM.
(3) Remove ignition coil from coil mounting
bracket (two bolts).
REMOVAL - 8.0L
Two separate coil packs containing a total of five
independent coils are attached to a common mount-
ing bracket located above the right engine valve
cover (Fig. 27). The front and rear coil packs can be
serviced separately.
(1) Remove the secondary spark plug cables from
the coil packs. Note position of cables before removal.
(2) Disconnect the primary wiring harness connec-
tors at coil packs.(3) Remove the four (4) coil pack-to-coil mounting
bracket bolts for the coil pack being serviced (Fig.
27).
(4) Remove coil(s) from mounting bracket.
INSTALLATION - 3.9L/5.2L/5.9L
The ignition coil is an epoxy filled type. If the coil
is replaced, it must be replaced with the same type.
(1) Install the ignition coil to coil bracket. If nuts
and bolts are used to secure coil to coil bracket,
tighten to 11 N´m (100 in. lbs.) torque. If the coil
mounting bracket has been tapped for coil mounting
bolts, tighten bolts to 5 N´m (50 in. lbs.) torque.
(2) Connect all wiring to ignition coil.
INSTALLATION - 8.0L
(1) Position coil packs to mounting bracket (prima-
ry wiring connectors face downward).
(2) Install coil pack mounting bolts. Tighten bolts
to 10 N´m (90 in. lbs.) torque.
(3) Install coil pack-to-engine mounting bracket (if
necessary).
(4) Connect primary wiring connectors to coil
packs (four wire connector to front coil pack and
three wire connector to rear coil pack).
(5) Connect secondary spark plug cables to coil
packs. Refer to (Fig. 28) for correct cable order.
Fig. 26 Ignition CoilÐ5.9L V-8 HDC-Gas Engine
1 - COIL MOUNTING BOLTS
2 - IGNITION COIL
3 - COIL ELEC. CONNECTOR
4 - SECONDARY CABLEFig. 27 Ignition Coil PacksÐ8.0L V-10 Engine
BR/BEIGNITION CONTROL 8I - 15
IGNITION COIL (Continued)

SPARK PLUG
DESCRIPTION
The 3.9L V-6 and 5.2L/5.9L V-8 engines use resis-
tor type spark plugs. The 8.0L V-10 engine uses
inductive type spark plugs.
Spark plug resistance values range from 6,000 to
20,000 ohms (when checked with at least a 1000 volt
spark plug tester).Do not use an ohmmeter to
check the resistance values of the spark plugs.
Inaccurate readings will result.
OPERATION
To prevent possible pre-ignition and/or mechanical
engine damage, the correct type/heat range/number
spark plug must be used.
Always use the recommended torque when tighten-
ing spark plugs. Incorrect torque can distort the
spark plug and change plug gap. It can also pull the
plug threads and do possible damage to both the
spark plug and the cylinder head.
Remove the spark plugs and examine them for
burned electrodes and fouled, cracked or broken por-
celain insulators. Keep plugs arranged in the order
in which they were removed from the engine. A sin-gle plug displaying an abnormal condition indicates
that a problem exists in the corresponding cylinder.
Replace spark plugs at the intervals recommended in
Group O, Lubrication and Maintenance
Spark plugs that have low mileage may be cleaned
and reused if not otherwise defective, carbon or oil
fouled. Also refer to Spark Plug Conditions.
CAUTION: Never use a motorized wire wheel brush
to clean the spark plugs. Metallic deposits will
remain on the spark plug insulator and will cause
plug misfire.
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. 29). 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.
Fig. 28 Spark Plug Cable OrderÐ8.0L V-10 Engine
Fig. 29 Normal Operation and Cold (Carbon) Fouling
1 - NORMAL
2 - DRY BLACK DEPOSITS
3 - COLD (CARBON) FOULING
8I - 16 IGNITION CONTROLBR/BE
IGNITION COIL (Continued)