Flowering can take a fair amount of energy from the pumpkin plant so I hit both plants with a very small amount of foliar RAW Bloom (3-12-12) this evening. A little nudge with phosphorous and potassium can encourage flowering. However, too much can change up the chemistry and give you the opposite effect.
I have to admit I'm getting a little impatient right now. Both of my plants have females on the main vine at around the 10 foot mark. However, I'd like to see my plants bigger before I pollinate a keeper. I'll pollinate everything because you never know what you'll get and what will take, but ideally I'd like to pollinate at around 14-16' range on the main this year. I'd also like to pollinate by the 24th if possible. Problem with that is that once a female shows up, depending on the weather (females seem to develop faster when it is hot out), it is typically 7-10 days until a female flower opens. That means I need females to show up tomorrow or the next day on the main vine.
When it comes to females it can really be hit or miss as to when they show up. When a plant is ready they will sometimes just start popping up all over the place. Some plants might just get a few females on it at all, so you take what you can get. I think a lack of flowering is sometimes a genetic thing and other times it is because of too much nitrogen in the soil or other imbalances. Nitrogen will encourage vining and the plant can't just can't switch to flowering mode if there is too much.
One thing you have to look at when it comes to newly pollinated pumpkins is their position on the vine. Ideally you want that pumpkin to be in a place where that vine won't get kinked or crushed by the pumpkin as it grows. It is hard to remember, but that pumpkin could be 4-5 feet across at the end of the season and if the pumpkin isn't positioned well, you will have all kinds of problems with the pumpkin trying to pick itself off the vine if it isn't positioned properly.