1998 DODGE RAM 1500 Spark plug

SPARK PLUG
DESCRIPTION
Resistor type spark plugs are used on all engines.
Sixteen spark plugs (2 per cylinder) are used with
5.7L V-8 engines.
DIAGNOSIS AND TESTING - SPARK PLUG
CONDITIONS
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
the Lubrication and Maintenance section.
Spark plugs that have low mileage may be cleaned
and reused if not otherwise defective, carbon or oil
fouled.
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.
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.
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. 23). 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. 23). 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. 24), evaluate engine condition for the
cause of oil entry into that particular combustion
chamber.
Fig. 23 NORMAL OPERATION AND COLD (CARBON)
FOULING
1 - NORMAL
2 - DRY BLACK DEPOSITS
3 - COLD (CARBON) FOULING
DRIGNITION CONTROL 8I - 17

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. 25).
This short circuits the electrodes. Spark plugs with
electrode gap bridging can be cleaned using standard
procedures.
SCAVENGER DEPOSITS
Fuel scavenger deposits may be either white or yel-
low (Fig. 26). They may appear to be harmful, but
this is a normal condition caused by chemical addi-
tives in certain fuels. These additives are designed to
change the chemical nature of deposits and decrease
spark plug misfire tendencies. Notice that accumula-
tion on the ground electrode and shell area may be
heavy, but the deposits are easily removed. Spark
plugs with scavenger deposits can be considered nor-
mal in condition and can be cleaned using standard
procedures.
CHIPPED ELECTRODE INSULATOR
A chipped electrode insulator usually results from
bending the center electrode while adjusting the
spark plug electrode gap. Under certain conditions,
severe detonation can also separate the insulator
from the center electrode (Fig. 27). Spark plugs with
this condition must be replaced.
PREIGNITION DAMAGE
Preignition damage is usually caused by excessive
combustion chamber temperature. The center elec-
trode dissolves first and the ground electrode dis-
solves somewhat latter (Fig. 28). Insulators appear
relatively deposit free. Determine if the spark plug
has the correct heat range rating for the engine.
Determine if ignition timing is over advanced or if
other operating conditions are causing engine over-
heating. (The heat range rating refers to the operat-
ing temperature of a particular type spark plug.
Spark plugs are designed to operate within specific
temperature ranges. This depends upon the thick-
ness and length of the center electrodes porcelain
insulator.)
Fig. 24 OIL OR ASH ENCRUSTED
Fig. 25 ELECTRODE GAP BRIDGING
1 - GROUND ELECTRODE
2 - DEPOSITS
3 - CENTER ELECTRODE
Fig. 26 SCAVENGER DEPOSITS
1 - GROUND ELECTRODE COVERED WITH WHITE OR YELLOW
DEPOSITS
2 - CENTER ELECTRODE
8I - 18 IGNITION CONTROLDR
SPARK PLUG (Continued)

SPARK PLUG OVERHEATING
Overheating is indicated by a white or gray center
electrode insulator that also appears blistered (Fig.
29). The increase in electrode gap will be consider-
ably in excess of 0.001 inch per 2000 miles of opera-
tion. This suggests that a plug with a cooler heat
range rating should be used. Over advanced ignition
timing, detonation and cooling system malfunctions
can also cause spark plug overheating.
REMOVAL
3.7L V-6
Each individual spark plug is located under each
ignition coil. Each individual ignition coil must be
removed to gain access to each spark plug. Refer to
Ignition Coil Removal/Installation.(1) Remove necessary air filter tubing at throttle
body.
(2) Prior to removing ignition coil, spray com-
pressed air around coil base at cylinder head.
(3) Prior to removing spark plug, spray com-
pressed air into cylinder head opening. This will help
prevent foreign material from entering combustion
chamber.
(4) Remove spark plug from cylinder head using a
quality socket with a rubber or foam insert. Also
check condition of ignition coil o-ring and replace as
necessary.
(5) Inspect spark plug condition. Refer to Diagnos-
tics and Testing - Spark Plug Conditions.
4.7L V-8
Each individual spark plug is located under each
ignition coil. Each individual ignition coil must be
removed to gain access to each spark plug. Refer to
Ignition Coil Removal/Installation.
(1) Remove necessary air filter tubing at throttle
body.
(2) Prior to removing ignition coil, spray com-
pressed air around coil base at cylinder head.
(3) Prior to removing spark plug, spray com-
pressed air into cylinder head opening. This will help
prevent foreign material from entering combustion
chamber.
(4) Remove spark plug from cylinder head using a
quality socket with a rubber or foam insert. Also
check condition of ignition coil o-ring and replace as
necessary.
(5) Inspect spark plug condition. Refer to Diagnos-
tics and Testing - Spark Plug Conditions.
5.7L V-8
Eight of the 16 spark plugs are located under an
ignition coil; the other 8 are not. If spark plug being
Fig. 27 CHIPPED ELECTRODE INSULATOR
1 - GROUND ELECTRODE
2 - CENTER ELECTRODE
3 - CHIPPED INSULATOR
Fig. 28 PREIGNITION DAMAGE
1 - GROUND ELECTRODE STARTING TO DISSOLVE
2 - CENTER ELECTRODE DISSOLVED
Fig. 29 SPARK PLUG OVERHEATING
1 - BLISTERED WHITE OR GRAY COLORED INSULATOR
DRIGNITION CONTROL 8I - 19
SPARK PLUG (Continued)

removed is under coil, coil must be removed to gain
access to spark plug. Refer to Ignition Coil Removal/
Installation and observe all CAUTIONS and WARN-
INGS.
Before removing or disconnecting any spark plug
cables, note their original position. Remove cables
one-at-a-time. To prevent ignition crossfire, spark
plug cablesMUSTbe placed in cable tray (routing
loom) into their original position. Refer to Spark Plug
Cable Removal for a graphic.
Before installing spark plug cables to either the
spark plugs or coils, apply dielectric grease to inside
of boots.
(1) Remove necessary air filter tubing at throttle
body.
(2) Prior to removing ignition coil (if coil removal
is necessary), spray compressed air around coil base
at cylinder head cover.
(3) Prior to removing spark plug, spray com-
pressed air into cylinder head opening. This will help
prevent foreign material from entering combustion
chamber.
(4) Remove spark plug from cylinder head using a
quality socket with a rubber or foam insert.
(5) Inspect spark plug condition. Refer to Diagnos-
tics and Testing - Spark Plug Conditions.
CLEANING
CLEANING AND ADJUSTMENT
The plugs may be cleaned using commercially
available spark plug cleaning equipment. After clean-
ing, file center electrode flat with a small point file or
jewelers file before adjusting gap.
CAUTION: Never use a motorized wire wheel brush
to clean spark plugs. Metallic deposits will remain
on spark plug insulator and will cause plug misfire.
Adjust spark plug gap with a gap gauging tool
(Fig. 30).
INSTALLATION
3.7L V-6
Special care should be taken when installing spark
plugs into the cylinder head spark plug wells. Be
sure the plugs do not drop into the plug wells as elec-
trodes can be damaged.
Always tighten spark plugs to the specified torque.
Over tightening can cause distortion resulting in a
change in the spark plug gap or a cracked porcelain
insulator.
(1) Start the spark plug into the cylinder head by
hand to avoid cross threading.(2) Tighten spark plugs. Refer to torque specifica-
tions.
(3) Before installing ignition coil(s), check condi-
tion of coil o-ring and replace as necessary. To aid in
coil installation, apply silicone to coil o-ring.
(4) Install ignition coil(s). Refer to Ignition Coil
Removal/Installation.
4.7L V-8
CAUTION: The 4.7L V±8 engine is equipped with
copper core ground electrode spark plugs. They
must be replaced with the same type/number spark
plug as the original. If another spark plug is substi-
tuted, pre-ignition will result.
Special care should be taken when installing spark
plugs into the cylinder head spark plug wells. Be
sure the plugs do not drop into the plug wells as elec-
trodes can be damaged.
Always tighten spark plugs to the specified torque.
Over tightening can cause distortion resulting in a
change in the spark plug gap or a cracked porcelain
insulator.
(1) Start the spark plug into the cylinder head by
hand to avoid cross threading.
(2) Tighten spark plugs. Refer to torque specifica-
tions.
(3) Before installing ignition coil(s), check condi-
tion of coil o-ring and replace as necessary. To aid in
coil installation, apply silicone to coil o-ring.
Fig. 30 SETTING SPARK PLUG GAP - TYPICAL
1 - GAUGE TOOL
2 - SPARK PLUG
8I - 20 IGNITION CONTROLDR
SPARK PLUG (Continued)

(4) Install ignition coil(s). Refer to Ignition Coil
Removal/Installation.
5.7L V-8
(1) Special care should be taken when installing
spark plugs into the cylinder head spark plug wells.
Be sure the plugs do not drop into the plug wells as
electrodes can be damaged.
(2) Start the spark plug into cylinder head by
hand to avoid cross threading aluminum threads. To
aid in installation, attach a piece of rubber hose, or
an old spark plug boot to spark plug.
(3) The 5.7L V-8 is equipped with torque critical
design spark plugs. Do not exceed 15 ft. lbs. torque.
Tighten spark plugs. Refer to torque specifications.
(4) Before installing spark plug cables to either the
spark plugs or coils, apply dielectric grease to inside
of boots.
(5) To prevent ignition crossfire, spark plug cables
MUSTbe placed in cable tray (routing loom) into
their original position. Refer to Spark Plug Cable
Removal for a graphic.
(6) Install ignition coil(s) to necessary spark plugs.
Refer to Ignition Coil Installation.
(7) Install spark plug cables to remaining spark
plugs. Remember to apply dielectric grease to inside
of boots.
IGNITION COIL CAPACITOR
DESCRIPTION
One coil capacitor is used. It is located in the right-
rear section of the engine compartment.
OPERATION
The coil capacitor(s) help dampen the amount of
conducted electrical noise to the camshaft position
sensor, crankshaft position sensor, and throttle posi-
tion sensor. This noise is generated on the 12V sup-
ply wire to the ignition coils and fuel injectors.
REMOVAL
The coil capacitor is located in the right-rear sec-
tion of the engine compartment. It is attached with a
mounting stud and nut.
(1) Disconnect electrical connector at capacitor
(Fig. 31).
(2) Remove mounting nut and remove ground
strap.
(3) Remove capacitor.
INSTALLATION
(1) Position capacitor to mounting stud.
(2) Position ground strap to mounting stud.
(3) Tighten nut to 7 N´m (60 in. lbs.) torque.
(4) Connect electrical connector to coil capacitor.
SPARK PLUG CABLE
DESCRIPTION
Spark plug cables are sometimes referred to as sec-
ondary ignition wires, or secondary ignition cables.
Plug cables are used only on the 5.7L V-8 engine.
OPERATION
The spark plug cables transfer electrical current
from the ignition coil(s) and/or distributor, to individ-
ual spark plugs at each cylinder. The resistive spark
plug cables are of nonmetallic construction. The
cables provide suppression of radio frequency emis-
sions from the ignition system.
Plug cables are used only on the 5.7L V-8 engine.
Fig. 31 CAPACITOR LOCATION
1 - COIL CAPACITOR
2 - MOUNTING STUD
3 - GROUND STRAP
4 - MOUNTING NUT
5 - ELEC. CONNECT.
DRIGNITION CONTROL 8I - 21
SPARK PLUG (Continued)

REMOVAL
5.7L V-8
Spark plug cables on the 5.7L engine are paired on
cylinders 1/6, 2/3, 4/7 and 5/8. Before removing or
disconnecting any spark plug cables, note their orig-
inal position (Fig. 32). Remove cables one-at-a-time.
To prevent ignition crossfire, spark plug cables
MUSTbe placed in cable tray (routing loom) into
their original position. The cable retention clips (Fig.
32) must also be securly locked.
Before installing spark plug cables to either the
spark plugs or coils, apply dielectric grease to inside
of boots.
If cable tray removal is necessary, release the 4
tray-to-manifold retention clips (Fig. 32).
INSTALLATION
Install cables into the proper engine cylinder firing
order sequence. Refer to Specifications.
When replacing the spark plug and coil cables,
route the cables correctly and secure them in the
proper retainers. Failure to route the cables properly
may cause the radio to reproduce ignition noise. It
could also cause cross-ignition of the plugs, or, may
short-circuit the cables to ground.
When installing new cables, make sure a positive
connection is made. A snap should be felt when a
good connection is made.
5.7L V-8
Refer to Spark Plug Cable Removal for
information.
Fig. 32 5.7L SPARK PLUG CABLE ROUTING
1 - #8 COIL-TO- #5 SPARK PLUG (MARKED 5/8) 7 - CABLE TRAY
2 - #5 COIL-TO- #8 SPARK PLUG (MARKED 5/8) 8 - CLIPS (SPARK PLUG CABLE-TO-TRAY- RETENTION)
3 - #7 COIL-TO- #4 SPARK PLUG (MARKED 4/7) 9 - #2 COIL-TO- #3 SPARK PLUG (MARKED 2/3)
4 - #3 COIL-TO- #2 SPARK PLUG (MARKED 2/3) 10 - #6 COIL-TO- #1 SPARK PLUG (MARKED 1/6)
5 - #1 COIL-TO- #6 SPARK PLUG (MARKED 1/6) 11 - #4 COIL-TO- #7 SPARK PLUG (MARKED 4/7)
6 - CLIPS (TRAY-TO-MANIFOLD RETENTION)
8I - 22 IGNITION CONTROLDR
SPARK PLUG CABLE (Continued)

DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - ENGINE
DIAGNOSIS - INTRODUCTION
Engine diagnosis is helpful in determining the
causes of malfunctions not detected and remedied by
routine maintenance.
These malfunctions may be classified as either per-
formance (e.g., engine idles rough and stalls) or
mechanical (e.g., a strange noise).
(Refer to 9 - ENGINE - DIAGNOSIS AND TEST-
ING) - PERFORMANCE and (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)ÐMECHANICAL for
possible causes and corrections of malfunctions.
(Refer to 14 - FUEL SYSTEM/FUEL DELIVERY -
DIAGNOSIS AND TESTING) and (Refer to 14 -
FUEL SYSTEM/FUEL INJECTION - DIAGNOSIS
AND TESTING) for the fuel system diagnosis.Additional tests and diagnostic procedures may be
necessary for specific engine malfunctions that can
not be isolated with the Service Diagnosis charts.
Information concerning additional tests and diagno-
sis is provided within the following diagnosis:
²Cylinder Compression Pressure Test (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
²Cylinder Combustion Pressure Leakage Test
(Refer to 9 - ENGINE - DIAGNOSIS AND TEST-
ING).
²Engine Cylinder Head Gasket Failure Diagnosis
(Refer to 9 - ENGINE/CYLINDER HEAD - DIAGNO-
SIS AND TESTING).
²Intake Manifold Leakage Diagnosis (Refer to 9 -
ENGINE/MANIFOLDS/INTAKE MANIFOLD -
DIAGNOSIS AND TESTING).
DIAGNOSIS AND TESTING - ENGINE DIAGNOSIS - PERFORMANCE
CONDITION POSSIBLE CAUSE CORRECTION
ENGINE WILL NOT START 1. Weak battery 1. Charge or replace as necessary.
2. Corroded or loose battery
connections.2. Clean and tighten battery
connections. Apply a coat of light
mineral grease to the terminals.
3. Faulty starter. 3. (Refer to 8 - ELECTRICAL/
STARTING - DIAGNOSIS AND
TESTING).
4. Faulty coil or control unit. 4. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).
5. Incorrect spark plug gap. 5. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING).
6. Incorrect right bank cam timing. 6. Refer to engine timing in this
section.
7. Dirt or water in fuel system. 7. Clean system and replace fuel
filter.
8.Faulty fuel pump, relay or wiring. 8.Repair or replace as necessary.
9. Faulty cam or crank sensor 9. Refer to Ignition system.
ENGINE STALLS OR ROUGH IDLE 1. Vacuum leak. 1. Inspect intake manifold and
vacuum hoses, repair or replace as
necessary.
2. Faulty crank position sensor 2. Replace crank position sensor.
3. Faulty coil. 3. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).
9 - 4 ENGINE - 3.7LDR
ENGINE - 3.7L (Continued)

CONDITION POSSIBLE CAUSE CORRECTION
4. Incorrect cam timing. 4. (Refer to 9 - ENGINE/VALVE
TIMING - STANDARD
PROCEDURE).
1. ENGINE LOSS OF POWER 1. Dirty or incorrectly gapped spark
plugs.1. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING).
2. Dirt or water in fuel system. 2. Clean system and replace fuel
filter.
3. Faulty fuel pump. 3. (Refer to 14 - FUEL SYSTEM/
FUEL DELIVERY/FUEL PUMP -
DIAGNOSIS AND TESTING).
4. Blown cylinder head gasket. 4. Replace cylinder head gasket.
5. Low compression. 5. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING), repair
as necessary.
6. Burned, warped or pitted valves. 6. Replace as necessary.
7. Plugged or restricted exhaust
system.7. Inspect and replace as
necessary.
8. Faulty coil. 8. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).
9. Incorrect cam timing. 9. Refer to Engine TIming in this
section.
1. ENGINE MISSES ON
ACCELERATION1. Spark plugs dirty or incorrectly
gapped.1. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING).
2. Dirt in fuel system. 2. Clean fuel system.
3. Burned, warped or pitted valves. 3. Replcae as necessary.
4. Faulty coil. 4. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).
1. ENGINE MISSES AT HIGH
SPEED1. Spark plugs dirty or incorrectly
gapped.1. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING).
2. Faulty coil. 2. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).
3. Dirt or water in fuel system. 3. Clean system and replace fuel
filter.
DRENGINE - 3.7L 9 - 5
ENGINE - 3.7L (Continued)