Intermittent Failure Diagnosis - Jeep J-10 Series 1982 Technical & Service Manual

CAUTION: Do not remove wires from spark plugs for
cylinders lor 5 ofa six-cylinder engine orfor cylinders 8
or $ of an eight-cylinder engine when performing this
test, otherwise pickup coil may be damaged.
(3) Connect ignition coil wire to distributor cap. Re
move wire from one spark plug.
(4) Use insulated pliers to hold wire 1/2 inch from
engine cylinder head or block while rotating engine with
starter motor. Observe wire terminal for arc.
(a) If arc occurs, inspect for fuel system prob
lems or incorrect ignition timing.
(b) If no arc occurs, inspect for defective rotor
or distributor cap, or defective spark plug wires.
(5) If no arc occurs from ignition coil wire terminal,
test coil secondary winding resistance. It should not
exceed 10,000 ohms. Replace if required.
(6) Read following notes and proceed to SSI System
Diagnosis and Repair Simplification (DARS) Chart 1.
IGNITION SYSTEMS 1G-15
NOTE: The DARS charts are organized to permit test
ing of the primary sub-circuit separately and in the
most logical sequence. When the problem is located, it is
not necessary to perform additional tests.
NOTE: Ifa particularcomponent or sub-circuit is sus
pected, locate the applicable DARS Chart andfollow the
procedures outlined. Ifno particularcomponent or sub-
circuit is suspected, begin with Chart 1 and proceed
from chart to chart until the problem is located.
NOTE: Do not perform Chart k tests until after Chart 1
tests have been completed.
Intermittent Failure Diagnosis
Intermittent failure may be caused by loose or cor
roded terminals, defective or missing components, poor
ground connections or defective wiring. Refer to the
Service Diagnosis chart.
Service Diagnosis
Condition Possible Cause
Correction
ENGINE FAILS TO
START (NO SPARK
(1)
No voltage to ignition system.
(1)
Check battery, ignition switch and
wiring. Repair as required.
AT PLUGS)
(2) Electronic Control Unit ground
wires inside distributor open,
loose or corroded.
(2)
Clean, tighten or repair as required.
(3)
Primary wiring connectors not
fully engaged.
(3)
Clean and fully engage connectors.
(4)
Ignition coil open or shorted.
(4)
Test coil. Replace if faulty.
(5) Electronic Control Unit defective.
(5)
Replace Electronic Control Unit.
«.
(6)
Cracked distributor cap.
(6)
Replace cap.
(7) Defective rotor.
(7)
Replace rotor.
ENGINE BACKFIRES
BUT FAILS TO START
(1)
(2)
Incorrect ignition timing.
Moisture in distributor.
(1)
(2)
Check timing. Adjust as required.
Dry cap and rotor.
(3)
Distributor cap faulty.
(3)
Check cap for loose terminals,
cracks and dirt. Clean or replace
as required.
(4)
Ignition wires not connected in
correct firing order.
(4) Connect in correct order.
ENGINE RUNS ONLY
WITH KEY IN START
POSITION
(1)
Open in resistance wire or
excessive resistance.
(1)
Replace resistance wire and harness
assembly.
ENGINE CONTINUES
TO RUN WITH KEY
OFF
(1)
(2)
Defective starter motor solenoid.
Shorted diode in alternator
warning lamp circuit
(1)
(2)
Replace solenoid.
Replace diode.
70866A