The vehicle heater described has a burner supplied from a tank through a fuel line to which a pressure-controlled fuel pump (2) and a solenoid valve (24) are connected. The solenoid valve offers a relatively high resistance to the flow of fuel. The pressure in the pump delivery line thus drops relatively slowly. If vapor/gas forms in the fuel line (L2, L3, L4) due to overheating, it must be driven out of the line as rapidly as possible when the heater is switched on. The solenoid valve (24) offers only a low resistance to air/vapor/gas, resulting in a rapid drop in pressure at the pump delivery outlet and hence an increase in pump frequency (i.e. pump performance). The gas is therefore driven very rapidly out of the line between the pump and the burner, thus avoiding any interruptions in operations due to gas/vapor which has collected in the fuel line.