A valve assembly is used to start an engine with a minimum of electrical power. The valve assembly provides a low initial fuel flow rate to the engine. Upon initiation of combustion in an engine combustion chamber, the resulting increase in fluid pressure is transmitted through the flow of fuel to the valve assembly. The pressure transmitted from the combustion chamber is effective to actuate the valve assembly to increase the rate of flow of fuel to the engine. The valve assembly includes an inlet valve which is opened to enable fuel to flow at a relatively low rate through an initial flow control orifice to the engine combustion chamber. Upon initiation of burning of fuel, the increase in pressure is transmitted to the valve assembly and is effective to move a main valve member to open a variable size main flow control orifice. Opening of the variable size main flow control orifice increases the rate of flow of fuel to the combustion chamber.