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scratch is present on the cylinder wall. Pearl overheating check if the spark plug type matches, and then replace with the spark plug with lower heat value (rapid heat radiation). 11.6 Regular replacement and use overdue The spark plug is the low-value consumption goods. Though cheaper compared with other matching parts, its ignition performance directly affects the performance of the engine. Therefore, it needs regular replacement. For the spark plug used in our vehicles, we suggest that you should replace the spark plug at the following mileages: 10,000-15,000 km (single electrode); 15,000-25,000 km (multi electrode). Ignition performance fall of spark plug will make fuel consumption rise and power drop off. The economic loss caused by excessive fuel consumption unconsciously will even afford to hundreds of new spark plugs. Use overdue makes the working condition of the engine poor in long term and brings some damage to the engine. 11.7 Inspection and maintenance of the spark plug The inspection items for spark plug mainly include carbon deposit, electrode burn through, gap, and sealing and spark jump performances of the spark plug etc. The electrode gap of the spark plug should be 0.7-0.9mm. Too small electrode gap will reduce the breakdown voltage and weaken the spark intensity; while too big electrode gap will increase the voltage required by the spark plug and cause spark out, especially when the ignition coil is aging and the ignition system is in poor maintenance, spark out is more liable to occur. Common failures of spark plug: fall in sealing performance, air leak and soot at the air leakage position. The above failures can be inspected and judged through sealing performance test and spark jump test. Both sealing performance test and spark jump test can be conducted on a spark plug cleaning tester. It is unscientific that some drivers and maintenance professionals remove the spark plug from the engine, place it on the cylinder head and inspect if it is in sound conditions using high voltage of the vehicle. In this test, the spark plug electrode is under an atmosphere other than a gas pressure of over 800KPa, its working pressure. Therefore, spark jump of a spark plug under an atmosphere does not indicate that it will also reliably produce spark jump under a high pressure conditions in the cylinder. It is required that carbon deposit disposal and proper adjustment of spark plug gap should be done after a mileage of 10,000-15,000 km in its lifetime. When the temperature in cylinder rises, the electrode gap should be increased properly. That is, increase the electrode gap in summer while reduce it in winter. If the mixed air is strong, the electrode gap should be increased; otherwise, decreased. In plain region, the electrode gap should be decreased while in plateau region, increased. 12. Carbon Canister Solenoid Valve Control 12.1 Function: Carbon canister solenoid valve is a device used to enable the fuel steam in fuel tank to enter cylinder to combust through control of ECU. Through controlling duty cycle of a solenoid valve, ECU can accomplish open and close of the solenoid valve. 12.2 Working principle: The canister control valve is composed of solenoid, armature iron and valve etc. There is a filter net at the inlet. The airflow through the canister control valve at one hand depends on the duty cycle of the electric pulse output of canister control valve by ECU, and at another hand depends on the |