INSPECTION
Check electrodes and inner and outer porcelain of plugs, noting the type of deposits and the degree of electrode erosion.
Scheme 8
Scheme 9
Scheme 10
Scheme 11
Scheme 12
- 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 city, weak ignition, too rich fuel mixture, dirty air cleaner, etc. It is advisable to replace with plugs having hotter heat range.
- 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.
- Overheating: White or light gray insulator with black or gray brown spots and bluish burnt electrodes indicate engine overheating. Moreover, the appearance results from incorrect ignition timing, loose spark plugs, wrong selection of fuel, hotter range plug, etc. It is advisable to replace with plugs having colder heat range.
Using tester, inspect the following items, and replace if defective.
- Secondary coil resistance
| CAUTION | If the resistance is extremely low, there is a short circuit. Ignitor is built-in the coil. Therefore, the resistance of the primary coil cannot be measured. |
Scheme 13
- Specified resistance: [Secondary side] Between (A) and (B) 12.8 kohms+/-15% Between (C) and (D) 12.8 kohms+/-15%
Check for
Scheme 14
- Damage to cords, deformation, burning or rust formation of terminals
- Resistance values of cords Resistance value: Except California model #1 cord: 5.6 - 10.6 kohms #2 cord: 7.3 - 13.7 kohms #3 cord: 5.9 - 11.1 kohms #4 cord: 7.3 - 13.7 kohms California model #1 cord: 7.6 - 12.7 kohms #2 cord: 7.6 - 12.7 kohms #3 cord: 7.5 - 12.7 kohms #4 cord: 7.5 - 12.7 kohms