In this paper, signed-rank based nonparametric detectors are used for pseudonoise (PN) code acquisition in frequency-selective Rician fading channels. We first derive the locally optimum rank detector and then propose the locally suboptimum rank (LSR) and kth order modified signed-rank (MSRk) detectors using approximate score functions. We compare the hybrid parallel double-dwell scheme using the LSR and MSRk detectors with that using the conventional squared-sum (SS) and modified sign (MS) detectors. From the simulation results, it is shown that the LSR and MSRk detectors perform better than the SS detector using the cell averaging constant false-alarm rate processor and the MS detector by about 2-3 dB.