Caught in a vicious sleep cycle!

My son is 14 mo today and we are caught in a vicious sleep cycle!  I can't break it!  He wakes up before 5 (4:30-4:45) some days and I try to leave him in crib until at least 5:30.  He is obviously not well rested b/c he is so whiney and cranky.  Rubbing eyes and tugging ears by 7 so he takes a very early morning nap (some days before 9) and...that's it.  I cannot seem to get him to take a PM nap.  A little history- he was always a bad sleeper.  Didn't sleep through night until 9 months or so after sleep training.  Before that he was waking at least 3 x.  Never a great napper.  Ever.  Back to today.  After that early morning nap I try to get him to take another.  And nothing.  It's either crying or playing in his crib.  So he starts showing signs of being tired by 4:30 and he's asleep at 6pm for the night.  He goes to bed beautifully, no tears, no screaming.  If we try to push bedtime later then all hell breaks loose b/c he is over tired.  So he's off to bed by 6, 6:30 the latest.  A good day he sleeps until 6am but that is rare.  Even 5 is ok b/c I totally get he is getting 11-12 hours.  But before 5 is just rough.  And the naps.  Oh the naps.  Any help.  Ive read Healthy Sleep Habits, Happy Child which helped trememndously with bedtime at night.  I think if the naps improved we might be on to something. Ive tried:

-timing the naps (ex, putting him in after so many hours of being awake)
-waiting for signs of sleepiness 
-not waiting for signs of sleepiness
-walks in stroller
-rides in car