The passion fruit is a subtropical to tropical fruit grown on an evergreen climbing vine. There are two basic types, the yellow and the purple. Both have similar growth habits. The fruits are sweet, fruity, full of antioxidants and popular in Australia, New Zealand, Hawaii, Thailand and other countries where they grow easily. The plants grow quickly, forming flowers at each new growth node, but most are self-sterile, which means they need a little help with pollination.
Check to make sure that your passion vine is getting all its basic requirements. Look to see if the soil is loamy with good drainage and that the pH is around 6.5 to 7.5. Make sure it is getting an inch of water a week and fertilize every three months with a 10-5-20 (NPK) fertilizer as well as giving it a good pruning after two years of growth. Realize it will need at least two years of growing before you can expect to see fruit.
Provide a favorable habitat for small carpenter bees. For whatever reason, these bees are the best insect pollinators of the passion fruit flowers. Since the blossoms are self-sterile, they need the pollen from another plant, so make sure you have at least two vines. Carpenter bees like decaying wood to build their nests in, so you can distribute a few pieces around the base of the vines to provide a home and source of food for them.
In the absence of carpenter bees, the flowers can be hand pollinated. This can be accomplished by brushing the flower from one vine with a small soft paintbrush and then rubbing it over the stamen of the flowers on the other vine. Make sure to avoid watering after pollination or the pollen will simply be washed away.