if its old 2.5 diesel engine you need to swap leak off from no4 to no1 injector. to do it you need to discard small leak off pipe [from no4 to filter] and fit blank from no1 on to no4 injector[ where pipe was removed],then using new length of pipe fit it to no 1injector and fit other end to filter[ where original pipe was.]
k, January 2010