INSPECTION
Check the electrodes and inner and outer ceramic insulator of plugs, noting the type of deposits and the degree of electrode erosion.
Scheme 10
Scheme 11
Scheme 12
Scheme 13
- Normal: Brown to grayish-tan deposits and slight electrode wear indicate correct spark plug heat range.
- Carbon fouled: Dry fluffy carbon deposits on insulator and electrode are mostly caused by slow speed driving in the city, weak ignition, too rich fuel mixture and dirty air cleaner.
- Oil fouled: Wet black deposits show oil entrance into the combustion chamber through worn rings or pistons, or excessive clearance between valve guides and stems.
- Overheating
White or light gray insulator with black or brown spots and bluish burnt electrodes indicate engine overheating, incorrect ignition timing, wrong selection of fuel, and loose spark plugs.
Scheme 14
Check the secondary coil resistance using a tester. Replace if defective.
| CAUTION | If the resistance is extremely low, it indicates the presence of a short-circuit. Ignitor is integrated with the coil. Therefore the resistance of primary side coil cannot be measured. |
Specified resistance
Secondary side
Between (A) and (B)
11.2 kohms ± 15%
Between (C) and (D)
11.2 kohms ± 15%
Scheme 15
Check the following items.
- Damage to cords, deformation, burning or rust formation of terminals
- Resistance value of cords
Specified resistance
#1 cord: 7.1 - 12.1 kohms
#2 cord: 12.1 - 19.9 kohms
#3 cord: 7.7 - 13.0 kohms
#4 cord: 12.3 - 20.2 kohms
