NANO

242 ENGINE 273 MPFI Spark Plug Defects The condition of spark plug firing ends can act as a guide to the state of tune and general condition of the engine. Normal Deposits Core nose lightly coated with grey-brown deposits. Electrodes not burning unduly - gap increasing about 0.01 mm per 2000 km (with the use of unleaded fuel). Spark plugs ideally suited to engine. Heavy Deposits Possible causes: Fuel or oil additives, Oil in combustion chamber, Worn valve guides. Replace spark plugs. Carbon Fouling Characterized by dull black sooty deposits although unleaded fuel carbon fouling can appear as glossy deposits similar in appearance to oil fouling. Deposits can short circuit the firing end; weakening or eliminating the spark. Check for clogged air filter. Replace spark plugs. Oil Fouling Deposits can short-circuit the firing end, weakening or eliminating the spark. May be caused by worn valve guides, bores or piston rings, or whilst a new or overhauled engine is running-in. Cure the oil problem, if possible. Temporary use of the next hotter grade of spark plug may stop the misfire. Replace spark plugs. Inspection: • Clean the spark plug by spark plug cleaner before measuring the gap. • Check the gap between center & body electrode with feeler gauge. It should be within specified limit. • Check the spark condition by spark plug tester. Fitment Procedure: • Fit the Spark plug with hand. Use wheel spanner & tighten it with specified torque 2.5 Kgf-m. CAUTION Ensure spark plug shouldn't be cross thread with cylinder head. • Fit the HT cable at spark plug end. CAUTION Hold the HT cable nearer to the end as shown • Ensure that other end of HT cable is properly located and connected to ignition coil. SPARK TEST • Disconnect injector connector. WARNING Without disconnection of injector connector, combustible gas may come out from spark plug holes during this test and may get ignited in engine room. • Remove spark plugs and connect them to high- tension cable, and then ground spark plugs. • Crank engine and check if each spark plug sparks. • If no spark is emitted, inspect high-tension cable, spark plugs, ignition coil, & power supply. Power Supply Check • Remove ignition coil connector. • Check tomake sure that coil terminals have battery voltage with ignition switch ON. • If no voltage or low voltage is found, check fuse, couplers and wiring harness.