Abstract: An improved ignition device wherein a spark plug is provided with a torch chamber surrounding the spark gap. A first mixture of fuel-rich fuel and air is supplied to the torch chamber where it is ignited by a spark and propelled as a jet of burning fuel into the combustion zone of a cylinder of an internal combustion engine. The burning fuel from the torch chamber provides suitable ignition of a relatively lean second mixture of fuel and air in the combustion chamber which mixture is leaner than would otherwise be suitably ignited with a spark from a conventional spark plug. A porous plug in the fuel line acts as a one-way valve by allowing liquid fuel to pass by capillary and/or seepage action while resisting backflow caused by periodic high pressures within the combustion chamber. A cooling and heat-shielding system protects the fuel supply system against excessive heat absorption which would tend to prematurely vaporize the fuel and interfere with the valving apparatus.