Spark plugs and ignition coils

Spark plugs and ignition coils

The air/ LPG mix in gas converted machines has a higher electrical resistance than the air/petrol mix in petrol generators. This results in higher voltages being generated in the ignition circuit and possible overheating of the spark plug or ignition coil. To counteract this effect the spark plug gap is reduced as much as possible (to about 0.4mm). Iridium type spark plugs that have conical electrodes are designed to further reduce the ignition circuit voltages. As Iridium spark plugs are very expensive it is probably more economical to reduce the gap on an ordinary spark plug and accept that they will need replacing more often than the plug on a petrol machine. In any case, whenever an LPG machine starts to misbehave the first thing to do is to change the spark plug and check that the gap is reduced to about 0.4mm.