Fuel pumping system for a gas turbine engine

A fuel supply system (50) for a gas turbine engine (40) has a first pump (26) for delivering fuel to a first use (72) on a gas turbine engine, and a second pump (24) for delivering fuel to a second use on the gas turbine engine. A valve (52) allows flow from the first pump to be delivered to the first use, but also routes some flow from the first pump to supplement fuel flow from the second pump until a pressure downstream of the second pump increases. The valve then allows flow from the second pump to flow to the first use to supplement the flow from the first pump.