Engine diagnostics by the appearance of spark plugs (Renault Logan 1)

1. Normal candle.

Brown or grayish-yellowish color and slight wear of the electrodes. Exact match of the heat value of the spark plug to the engine and operating conditions.

Note: When replacing spark plugs with new ones, install spark plugs with the same characteristics from those recommended by the manufacturer.

2. Soot deposits.

Dry soot deposits indicate a rich air-fuel mixture or late ignition. Causes misfires, difficult starting and erratic engine operation. Check for clogged air filter, coolant temperature and intake air temperature sensors.

Note: Use a "hotter" spark plug.

3. Oil deposits.

Oily electrodes and spark plug insulator. Cause: oil getting into the combustion chamber. Oil gets into the combustion chamber through valve guides or piston rings. Causes difficult starting, cylinder misfires and "twitching" of the running engine. Repair of the cylinder head and piston group of the engine is required. Replace the spark plugs.

4. Metal-containing plaque.

Brick-red iron oxide deposits on the insulator skirt from anti-knock iron-containing additives (ferrocene) to gasoline. They are deposited in an even, dense layer. When the engine is running under heavy load, under the influence of high temperature and pressure in the combustion chamber, the oxides are reduced to conductive paths of pure iron, shorting the central electrode to ground. This causes misfires and, as a result, a drop in engine power and increased fuel consumption. In addition, the catalytic converter of exhaust gases can be damaged, overheating greatly when gasoline that has not burned in the engine cylinders gets into it. The deposit is practically impossible to remove mechanically and does not burn out during prolonged movement at high speed. If this deposit appears on new spark plugs after a short mileage, change the refueling location.



Article reprinted from the website www.Renaultbook.ru

Note: If you cannot immediately replace the spark plugs with new ones, try to remove this deposit by soaking the spark plugs with their insulator skirts in phosphoric acid or a rust converter for ten minutes (contains orthophosphoric acid). After this, clean off the plaque with a non-metallic brush (you can use an old toothbrush) and wash the spark plugs first with water and then with gasoline.

5. Early ignition.

Melted electrodes. The insulator is white, but may be contaminated due to spark misfires and deposits from the combustion chamber. May cause engine damage. It is necessary to check the spark plug type, the cleanliness of the injector nozzles and fuel filter, the operation of the cooling and lubrication systems.

6. Detonation.

The insulator may be cracked or chipped. This may cause damage to the piston. Make sure the octane rating of the gasoline is correct.

7. Mechanical damage.

Damage can be caused by foreign objects entering the combustion chamber, and if a plug is used that is too long, its electrodes can snag the piston. This causes the plug to fracture, disable the cylinder and can damage the piston. Remove the foreign object from the cylinder and/or replace the plug.