A gear pump includes a valve member adapted to engage a valve seat and close a control port and urged to an open position by a coil spring. In order to reduce cocking of the valve member relative to the valve seat when the valve member is closed, the end coil of the spring that engages the valve member is formed so as to be in non-parallel relation with the sealing surface of the valve seat when the spring is relaxed. As the spring is compressed during closure of the valve member, the end coil moves into parallelism with the sealing surface in order to enable the valve member to squarely engage the sealing surface.