Verify and diagnose
• Visual inspection
• Vacuum test
• Cylinder/power balance
• Check cooling system operation
• Test fuel pressure and regulator
• Safety check
• Exhaust diagnose – sound, color, smell
• ook for symptoms or clues to diagnosis
Tune up procedure
• Check belts and hoses
• Check E!"
• Check battery and ser#ice as needed
• "emo#e and read plugs
• Compression test
• Check primary circuit and pulse
• Check coil
• Check plugs wire for resistance and damage
• $nspect cap and rotor
• Check %CV
Spark plugs
• Construction
• &iring/operation
• 'eat range
• (anufactures
• Type of plugs
• )iagnosis
• Terminal
• $nsulator
• Center electrode
• !round electrode
• *ir gap
• "esistor
• "each
Firing/operation
• Voltage/current enters from coil and plug wire to top terminal of plug
• $nsulated positi#e core conducts to positi#e electrode exposed in cylinder+
• Current always flows to ground – ,umps gay to ground electrode+
• Exposes fuel and air to spark and ignites mixture+
Plug types
• -hat do the numbers on the side of a plug mean.
• Si/e
• seat type
• reach and thread type
• heat range
• tip construction
• type / manufacture
Plug reach
• reach is the length of the threaded portion of the plug
• plugs ha#e to ha#e the correct reach into the cylinder
• Too long and the threads will hold heat and may cause pre0ignition+ %lug will
strip threads
• Too short – misfire
• Spark shrouded in a pocket
Heat range
• -hat makes a plug hot or cold.
• 1ot the intensity of the spark
• The length of the insulator and path to cooling
• Cold plug 2 short insulator 34uick to cooling5
• 'ot plug 2 long insulator 3longer to cooling5
Plug tip type
• "egular tip – standard
• Extended tip0fouling resistant
• V0groo#e
• Split fire
• 6 prong ground
• 7 prong ground
• (ultiple ground tip plugs ha#e been around since the 896:;s
• *ll ha#e some benefit – but no matter what it will find the easiest path to
ground
Plug types
• Standard copper plugs
o !ood conductibility
o Shorter life
o $nexpensi#e
o Some shrouding
o 'igher #oltage re4uirement
o <:k miles
• 1ickel plugs
o 'arder = better then copper >6?09@?
o !ood heat endurance
o onger lasting
o !ood conductor
• !old palladium 3positi#e electrode only5
o Aetter conductibility
o &ouling resistant
o (elts when o#erheats
• %latinum plugs
o Aest
o %latinum much harder then copper, nickel, or gold
o onger wear
o B:k – C:k miles
o &ine tip self cleans
• )ouble platinum plug
o )urable platinum tips
o Aoth positi#e and ground electrode platinum
o onger life+
o (ore expensi#e
o !ap pre0set
• &ull field
o no ground electrode
• $ridium plugs
o 'arder substance then platinum
o onger plug life
o (ore expensi#e
o Thinner #oltage re4uirement
o ess #oltage re4uirement
o 'igh compression / re##ing