A memory efficient test pattern generator for path delay faults, DTPG, is presented in this paper, which uses the efficient path identifier to represent a path. A compact bit table, path information table, is proposed to store test information efficiently. Furthermore, DTPG is capable of identifying functional sensitizable paths, which account for large percent of paths in many circuits. The experimental results show that DTPG is memory efficient. It generates tests for C3540 with 57 million paths and preserves the testability information for all paths. Experimental results show the influence of stepwise mandatory sensitization, multiple backtrace, and backtracking limits on the cpu time consumed by delay test generation process.