The /j/ sound is spelled with <y> when it occurs initially and is heard sometimes in initial <u> or <ew>.
As /j/ is fairly rare, only occurring in 3518 words in the dictionary, this was an easy list to work out manually. /j/ only occurs initially or in intial consonant clusters. The pairs I have collected below apply to RP, and do not take account of the variation that affects some US accents in which /ju/ may be replaced by /u/, as in a word like tune. The contrast is a known source of difficulty for Japanese speakers.
The density value is 3%. The list makes 66 semantic distinctions, a loading of 63%.
adieu ado beauty booty collier collar cue coo cues coos cuing cooing cued cooed cute coot dew do due do dune Doone ewe ooh ewes ooze feud food feuds foods fuel fool fuels fools fuelling fooling fuelled fooled hew who hews whose hue who hues whose Hugh who knew gnu lute loot mew moo mews moos mule moule mules moules muse moos mute moot mutes moots new gnu news gnus overdue overdo pew pooh pews poohs pewter Pooter pule pool pules pools puling pooling pure poor purely poorly purer poorer Q coo Q's coos queue coo queues coos queuing cooing queued cooed sue Sue tutor tooter U ooh undue undo U's ooze use ooze used oozed using oozing uses oozes yah are yaks axe yam am yank ankh yanks ankhs yapped apt yaps apse Yate ate yaw awe yaws awes yawed awed yaw or yaw ore yaws ores yawl awl yawls awls yawning awning yea A year err years errs yearn earn yearns earns yearned earned yearning eraning yearn urn yearns urns yeast east yell ell yells ells yet ate yield eeled yew ooh yews ooze yoke oak yokes oaks yoked oaked yoking oaking yolk oak yolks oaks you ooh your awe yours awes your or your ore yours ores
John Higgins, Shaftesbury, December 2010.