Fuel Delivery Valves
Fuel delivery valves are located on injection pump. Their main function is to ensure fuel injectors close quickly after injecting fuel. This prevents fuel dribble, which can cause pre-ignition problems and high emissions. See Fig 1 .
When fuel injection starts, the delivery valve opens allowing pressurized fuel from injection pump to flow to fuel injectors. As fuel injection ends, the fuel delivery valve closes, trapping fuel in the injection line. The force of a spring inside fuel delivery valve pushes valve farther into its seat causing trapped fuel to expand. This sudden drop in pressure, caused by expanding fuel, allows fuel injector to snap shut.