Embodiments of injectors suitable for injection ports having relatively small diameters are disclosed herein. An injector according to one embodiment includes a body having a first end portion opposite a second end portion. The second end portion is configured to be positioned adjacent to a combustion chamber and the first end portion is configured to be spaced apart from the combustion chamber. The injector also includes an ignition conductor extending through the body from the first end portion to the second end portion, and an insulator extending longitudinally along the ignition conductor and surrounding at least a portion of the ignition conductor. The injector further includes a valve extending longitudinally along the insulator from the first end portion to the second end portion. The valve includes a sealing end portion, and the valve is movable along the insulator between an open position and a closed position. The injector also includes a valve seat at or proximate to the second end portion of the body. When the valve is in the open position the sealing end portion is spaced apart from the valve seat, and when the valve is in the closed position the sealing end portion contacts at least a portion of the valve seat.