INSPECTION
Check the electrodes and inner and outer ceramic insulator of plugs, noting the type of deposits and the degree of electrode erosion.
Identifying Electrodes And Inner And Outer Ceramic Insulator Of Plugs. Scheme 10
Scheme 11
Scheme 12
Scheme 13
- Normal: Brown to grayish-tan deposits and slight electrode wear indicate correct spark plug heat range. (Scheme 11): Identifying Spark Plug Condition - Normal
- 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, dirty air cleaner, etc. (Scheme 12): Identifying Spark Plug Condition - Carbon Fouled
- Oil fouled: Wet black deposits show excessive oil entrance into combustion chamber through worn rings and pistons or excessive clearance between valve guides and stems. (Scheme 13): Identifying Spark Plug Condition - Oil Fouled
- Overheating
White or light gray insulator with black or brown spots and bluish burnt electrodes indicate engine overheating. Moreover, those appearance also results from incorrect ignition timing, loose spark plugs, wrong selection of fuel, or plug with too low a degree of heat durability, etc.
Identifying Spark Plug Condition - Overheating. Scheme 14
Check the following items using a tester. Replace if defective.
- Secondary coil resistance
| 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)
11.7 kohms ± 15%
Between (C) and (D)
11.7 kohms ± 15%
Locating Spark Plug Cords. Scheme 15
Check the following item.
- 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
