IGNITION SYSTEM SERVICE

TESTING AND REPAIR l Evaluate the symptoms –Narrow down possibilities l Pinpoint to a specific engine system –Compression –Fuel –Ignition l Perform basic tests first –Visually inspect

PRELIMINARY TESTS l Look for obvious problems –Loose Connections –Cracked components –Deteriorated/Burned components –Inspect other systems l Do you have a “dead cylinder”? –Perform manual cylinder balance test –RPM will change if cylinder is good

SPARK INTENSITY TEST l Usually used with a No Start l Can be used to test component integrity l Install spark tester and observe spark

SPARK TEST RESULTS l Spark should be a good strong spark –Wide –Bright blue –Snapping electric arc l Is it weak at one spark plug or all?

SPARK PLUG SERVICE l Bad spark plugs can cause many problems –Misfiring –Lack of Power –Poor Fuel Economy –Hard Starting

SPARK PLUG PROBLEMS l Can become coated with ash, oil, and fuel additives l Electrodes can burn and widen gap l Electrodes can deteriorate with age or cylinder efficiency

SPARK PLUG REMOVAL l Number wires to cylinders l Grasp boot, not wire l Blow debris from hole l Do not mix up spark plugs l Inspect “Read” spark plugs

SPARK PLUG SERVICE l Clean spark plugs l Gap spark plug to specifications l Install Spark plugs

SECONDARY SERVICE l Remove Spark Plug wire l Test wire for high resistance –Not over 10,000 ohms per foot l Secondary insulation test –Grounded Probe –Spray water –Look at wires at night l Replacement of wires must be correctly done

DISTRIBUTOR CAP AND ROTOR l Must visually inspect cap and rotor l Can cause backfiring and misfire l Carbon arcing can cause problems l Cracks can cause problems

ELECTRONIC DISTRIBUTOR SERVICE l PICK UP COIL PROBLEMS –Can cause misfire, stalling, no-start, hesitation l PICK UP COIL TESTING –Use ohmmeter –Must measure to specifications –Wiggle and Tap test pick up coil –AC analog voltmeter test –Lab Scope

PICK UP COIL SERVICE l Follow procedures to replace l Some ignition systems pick up coil air gaps are adjustable

IGNITION TIMING l Initial (or base) timing l Must follow procedures exactly! Check Spec’s l Must set during tune up or if distributor has been removed l Must make sure advances not working during adjustment!

IGNITION TIMING ADJUSTMENT l Disable ignition advances l Hook up timing light l Adjusting timing causes pickup coil and electronic control unit to fire the ignition coil sooner or later. l Turning distributor housing against shaft rotation advances timing l Turning distributor housing with shaft rotation retards timing

IGNITION TIMING PROBLEMS l TIMING MUST BE EXACT! VERY IMPORTANT! l Too far advanced will cause “Pinging”, engine damage l Too far retarded will cause low power, poor mileage, engine damage

MEASURING IGNITION TIMING l Strobe type timing light l Magnetic timing probe l Usually connect light to number one cylinder l MUST DISABLE ADVANCE –Vacuum advance –Mechanical (centrifugal) advance timing –Computerized timing advances –Align timing marks to specifications

CHANGING IGNITION TIMING l Loosen distributor hold down bolt l Use distributor wrench if available l Engine rpm low l No advance operation l Align marks l Tighten hold down bolt l Double check timing