An injector for injecting a reagent into an exhaust stream includes an outer tube extending through an electromagnet and surrounding an inner tube. A first end of the inner tube is sealingly fixed to an inner surface of the outer tube. A guide member and an orifice plate are each sealingly fixed to the inner surface of the outer tube. A second end of the inner tube is aligned by the guide member. A moveable valve member includes a pintle head guided by the inner surface of the outer tube to align the valve member with an orifice extending through the orifice plate.