Electrical energy is transmitted from the ignition coil to the inside of combustion chamber via the spark plug cables and spark plug. Sparking occurs between spark plug firing tip and the ground electrode (aka spark plug gap), thus igniting the A/F mixture. An adequate amount of voltage must be supplied by the ignition system (ignition coil, spark plug cables, spark plugs) to generate a spark across the spark plug’s gap.
One of the cause of fouling is causeed a drop in electrical voltage supplied by the ignition system to the spark plug. When the fouling gets excessive, the electrical voltage supplied would be lower than the voltage required by the spark plug. This in turn causes the spark plug to misfire, between the centre electrode and side electrode. To ensure that the spark plug functions properly, sufficient voltage needs to be supplied to the spark plugs.
The other cause is spark plug operating temperature. The tip of the spark plug is the hottest part of the spark plug, the operating temperature is between 480o C and 855o C, as such the tip temperature is one of the cause of fouling that leads to misfiring. When the tip temperature is below 480o C, the tip is not enough to burn of the carbon deposits left behind during combustion thus causing fouling.
As a general rule, the spark plug voltage requirement increases during the engine’s increasing RPM and the voltage requirement is lower during starting, low temperature and high RPM engine conditions.
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