A fuel injector includes a needle valve including a spring-retaining section and a guide section that is adjacent to the spring-retaining section. The spring-retaining section includes an elongated portion and a flange that are together configured to support a spring assembly. The guide section includes a plurality of constricted portions alternatingly arranged with a plurality of expanded portions to define an undulating shape of the guide section. Each of the plurality of expanded portions includes a plurality of indentations to permit fuel to travel therealong to exit an outlet of the fuel injector. The guide section has a length that is substantially equal to a length of the spring-retaining section.