That is great that you got pumpkins from seeds 5 years or older; seed viability for pumpkins is said to be about 4 or 5 years. However, it appears that the pumpkin fruit aborting when small might be a pollination or growing condition issue. Sometimes developing fruit can abort if the plant is stressed or injured, especially high temperature (high 80s or 90s F in day, 70s at night). Drought or flood can also cause this symptom, as well as insect or disease damage. Check to make sure the soil pH is optimum. You might also try hand pollinating to help proper pollination.
That is great that you got pumpkins from seeds 5 years or older; seed viability for pumpkins is said to be about 4 or 5 years. However, it appears that the pumpkin fruit aborting when small might be a pollination or growing condition issue. Sometimes developing fruit can abort if the plant is stressed or injured, especially high temperature (high 80s or 90s F in day, 70s at night). Drought or flood can also cause this symptom, as well as insect or disease damage. Check to make sure the soil pH is optimum. You might also try hand pollinating to help proper pollination.