IGNITION SYSTEM SERVICE
TESTING AND REPAIR
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Evaluate the symptoms
– Narrow down possibilities
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Pinpoint to a specific engine system
– Compression
– Fuel
– Ignition
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Perform basic tests first
– Visually inspect
PRELIMINARY TESTS
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Look for obvious problems
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Loose Connections
Cracked components
Deteriorated/Burned components
Inspect other systems
Do you have a “dead cylinder”?
– Perform manual cylinder balance test
– RPM will change if cylinder is good
SPARK INTENSITY TEST
Usually used with a No Start
 Can be used to test component integrity
 Install spark tester and observe spark
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SPARK TEST RESULTS
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Spark should be a good strong spark
– Wide
– Bright blue
– Snapping electric arc
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Is it weak at one spark plug or all?
SPARK PLUG SERVICE
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Bad spark plugs can cause many
problems
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Misfiring
Lack of Power
Poor Fuel Economy
Hard Starting
SPARK PLUG PROBLEMS
Can become coated with ash, oil, and fuel
additives
 Electrodes can burn and widen gap
 Electrodes can deteriorate with age or
cylinder efficiency
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SPARK PLUG REMOVAL
Number wires to cylinders
 Grasp boot, not wire
 Blow debris from hole
 Do not mix up spark plugs
 Inspect “Read” spark plugs
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SPARK PLUG SERVICE
Clean spark plugs
 Gap spark plug to specifications
 Install Spark plugs
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SECONDARY SERVICE
Remove Spark Plug wire
 Test wire for high resistance
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– Not over 10,000 ohms per foot
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Secondary insulation test
– Grounded Probe
– Spray water
– Look at wires at night
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Replacement of wires must be correctly
done
DISTRIBUTOR CAP AND
ROTOR
Must visually inspect cap and rotor
 Can cause backfiring and misfire
 Carbon arcing can cause problems
 Cracks can cause problems
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ELECTRONIC
DISTRIBUTOR SERVICE
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PICK UP COIL PROBLEMS
– Can cause misfire, stalling, no-start,
hesitation
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PICK UP COIL TESTING
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Use ohmmeter
Must measure to specifications
Wiggle and Tap test pick up coil
AC analog voltmeter test
Lab Scope
PICK UP COIL SERVICE
Follow procedures to replace
 Some ignition systems pick up coil air
gaps are adjustable
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IGNITION TIMING
Initial (or base) timing
 Must follow procedures
exactly! Check Spec’s
 Must set during tune up or
if distributor has been
removed
 Must make sure advances
not working during
adjustment!
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IGNITION TIMING
ADJUSTMENT
Disable ignition advances
 Hook up timing light
 Adjusting timing causes pickup coil and
electronic control unit to fire the ignition
coil sooner or later.
 Turning distributor housing against shaft
rotation advances timing
 Turning distributor housing with shaft
rotation retards timing
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IGNITION TIMING
PROBLEMS
TIMING MUST BE EXACT! VERY
IMPORTANT!
 Too far advanced will cause “Pinging”,
engine damage
 Too far retarded will cause low power,
poor mileage, engine damage
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MEASURING IGNITION
TIMING
Strobe type timing light
 Magnetic timing probe
 Usually connect light to number one
cylinder
 MUST DISABLE ADVANCE
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Vacuum advance
Mechanical (centrifugal) advance timing
Computerized timing advances
Align timing marks to specifications
CHANGING IGNITION
TIMING
Loosen distributor hold down bolt
 Use distributor wrench if available
 Engine rpm low
 No advance operation
 Align marks
 Tighten hold down bolt
 Double check timing
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