Spark Plug Wires - Jeep 1979 CJ-5 Technical & Service Manual

I M S
GENERAL SERflGE AND DIAGNOSIS
E—Cold Fouling (or Carbon Fouling)
Cold fouling is basically a carbon deposit. Dry, black
appearance of one or two plugs in a set may be caused by
sticking valves or bad ignition leads. Fouling of the
entire set may be caused by a clogged air cleaner, a
sticking exhaust manifold heat valve or a faulty choke.
F—Overheating
Overheating is indicated by a dead white or gray in-
sulator which appears blistered. Electrode gap wear rate
will be considerably in excess of 0.001 inch per 1000
miles. This may suggest t h a t a cooler heat range should
be used. Overadvanced ignition timing, detonation and
cooling s y s t e m p r o b l e m s can also cause p l u g
overheating.
NOTE: Some fuel refiners are using a manganese addi-
tive (MMT) in unleaded fuel During combustion, MMT
fuel covers the entire tip of the spark plug with a rust-
colored deposit. This rust color may be misdiagnosed as
water in the combustion chamber. Spark plug perform-
ance is not affected by MMT deposits.
Spark Plug Wires
To remove wires from spark plugs, twist the rubber
protector boot slightly to break the seal. Grasp the boot
and pull it from the plug with steady, even pressure. Do
not pull on the wire itself as this will damage the wire.
To remove wires from the distributor cap or coil
tower, loosen the boot first, then grasp the upper part of
the boot and the wire and gently pull straight up.
Wire Test
Do not puncture the spark plug wires with a probe
while performing any test. This may cause a separation
in the conductor. Remove the suspected wire and use an
ohmmeter to test for resistance according to the length
of the particular wire.
Resistance Values
Inches Ohms
Oto 15 3,000 to 10,000
15 to 25 4,000 to 15,000
25 to 35 6,000 to 20,000
Over 35 8,000 to 25,000
60748
When installing spark plug wires and the coil high
tension wire, be certain a good tight connection is made
at the spark plug, distributor cap tower and coil tower.
The protector boots at the spark plugs and distributor
cap must fit tightly. A partially seated wire creates an
additional gap in the circuit and the resulting spark
jump will cause terminal corrosion and wire damage.
Ignition Coil
Always check a suspected defective ignition coil on the
vehicle. Since a coil may break down after it has reached
operating temperature, it is important that the coil be at
operating temperature when tests are made. Perform
the tests following the instructions of the particular test
equipment manufacturer.
Dlstrllitor
The distributor used on all engines is the solid state
type. Other than cap and rotor inspection as outlined in
Chapter B, there is no scheduled maintenance for this
distributor. Refer to Chapter 1G—Ignition System for
distributor service procedures.
Distributor Rotor
Visually inspect the rotor for cracks, evidence of burn-
ing or corrosion on the metal tip, or evidence of mechani-
cal interference with the cap (fig. 1A-4). Some burning is
normal on the end of the metal tip. The grease applied to
the rotor tip for radio interference suppression will ap-
pear charred. This is normal. Do not remove charred
grease. Inspect the spring for insufficient tension. Re-
place a rotor displaying any of the conditions shown.
INSUFFICIENT
SPRING
TENSION
CRACKS
ROTOR
TIP
CORRODED
70202
Fig. 1 1 4 Rotor Inspection
Distributor Cap
Remove the distributor cap and wipe clean with a dry
rag. Perforin a visual inspection for cracks, carbon run-
ners, broken towers, burned or eroded terminals and
damaged rotor button (fig. 1A-5). Replace cap displaying