SPARK Pll PLUG CONDITIONS FACTORS CAUSING TH I Plug Flash Over Dirty insulator tops oil dirt and Firing from upper shunt current to base of plug Th terminal to base of caused by failure of spark plug bo plug Oil or Carbon Fouling Wet black deposits on firing end of condition This is usually caused 1 tons cylinders or sticky valves Soft fluffy dry black carbon de rich mixture operation excessive i of automatic choke or faulty adju Hard baked on black carbon depo cold a plug Lead Fouling Light By products of combustion and ft powdery or shiny glazed a powder which may later melt a coating on firing end Normal Electrode Wear Due to intense heat pressure am with spark discharge the electrod Rapid Electrode Wear Condition may be caused by 1 leakage past threads and seat ga installation torque or damaged gas or 4 plug too hot for operatin Broken Upper Insula Careless removal or installation o tor Firing around shell crimp under load conditions Broken Lower Insula The cause is usually carelessnes tor Firing Tip bending of centerwire to adjust t gapping tool to exert pressure ag electrode or insulator when bend adjust the gap Fracture or breakage of lower ins ally occur if the engine has been causing severe and prolonged detc Damaged Shell Very seldom occurs but cause is a handling by applying excessive b This failure is usually in the forn the thread next to the seat gaske the hex CAUTION Before adjusting gap file center electrode flat In adjusting the spark plug gap never bend the center electrode which extends through the porcelain center Always make adjustment by bending the ground side electrode Installation I 1 Inspect spark plug hole threads and clean before installing plugs Corrosion deposits can be removed with a 14 nun x 1 25 SAE spark plug tap available through local jobbers or by using a small soft wire brush in an electric drill If a tap is used coat it with plenty of grease to catch j any chips CAUTION Use extreme care when using tap to prevent cross threading Also crank engine IG DIAGNOSIS S CONDITION CORRECTIVE ACTION noisture on insulator will Keep plugs wiped clean with cloth e above condition can be moistened with cleaning solvent Check ot spark plug boot and and replace if necessary plug indicate oil pumping Correct engine condition In most y worn piston rings pis cases plugs in this condition will be serviceable after proper cleaning and regapping posits usually indicate a If troubles are not eliminated use dling improper operation hotter type plug tment of carburetor sits result from use of too Use hotter type plug el additives deposited as Remove deposits by blast cleaning rid glaze on insulator tip If this is not possible plugs should be replaced corrosive gases together Plugs should be regapped every 5000 e wears and gap widens miles burned valves 2 gas Correct engine condition Install plugs skets due to insufficient to specified torque Use a new spark cet 3 too lean a mixture plug seat gasket each time a new or g speeds and loads cleaned spark plug is installed Use colder type plug if condition continues to exist spark plug Replace with a new spark plug in regapping by either Replace with a new spark plug he gap or permitting the inst the tip of the center ing the side electrode to alator may also accasion Use colder type plug for the particu perated under conditions lar type of operation nation or pre ignition Imost always due to mis Replace with a new spark plug rque during installation i of a crack in the Vee of t or at the groove below several times to blow out any material dislodged during cleaning operation 2 Install spark plugs to engine using new gaskets and tighten to 20 25 ft lbs torque NOTE Do not use any anti seize compound on spark plug threads as this will act as an insulator and not allow proper spark plug cooling Be careful when installing plug to prevent gasket from falling into engine shroud assembly It may be desirable to use a spark plug socket that is equipped with an internal O ring seal to grip the spark plug or to fabricate a tool as shown in Figure 8 62 to start the plug into the cylinder head to avoid the possibility of dropping plugs into engine shroud assembly r AIR SFIOP MANUAL