Rail, Fuel: Operation
WARNING: This page is about a different car, the 2017 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
The stored volume of high pressure fuel inside the fuel rail helps to stabilize and equalize pressure fluctuations which result because of pulsations in the supply from the injector pump as well as due to the brief and repetitive extractions of fuel injector firing. The rail primarily influences the atomization of fuel at the injector nozzle, and the accuracy of the injected fuel quantity during injection.