Ditching the sleep crutch

My LO is 17 weeks and he sucks at napping. At night I can put him down, awake and he will fall asleep and sleep well all night, sometimes sleeping straight for 10.5 hours. During the day though he refuses to nap unless being pushed in the stroller. Once asleep he will usually stay asleep for 1-2 hours (if the movement continues). He will go to sleep by bouncing and being put in his crib, but will only stay down For about 15-20 minutes. We swaddle him at night and for naps in the crib but it only seems to work at night. Any advice for nap time that may help us through this without having to push him around in his stroller for hours? I want to develop a sleep schedule but this really hinders the schedule.