Florida shallow well pump - Losing prime while running

I just replaced my shallow well pump with a 1hp Sta-Rite pump. There are no leaks in the plumbing (using a pvc check valve), however it will not hold a prime.

Also, once it's primed and running, I can open the bib on the discharge end and get a great water flow, but when I close the bib and turn on the sprinkler system, I get a good burst of water (using the 2 gal bladder tank) then it takes a few seconds for the sprinkers to pop back up and run. The sprinklers run for about 5 minutes at full force then slowly for the next 2-10 minutes slow down and just barely drip water. I can then open the hose bib and get a good flow of water from the bib in about 30 seconds and the sprinklers run full force again while water is gushing out of the discharge bib. I can't for the life of me figure this out...

Any help before I have to call someone out?

Thanks

Are you having to actually re-prime the pump to get it going again, or are you only stopping the flow and waiting for it to catch up?

I am not a pump expert, but it sounds to me like your demand is occasionally greater than your supply.

I would get me a good check valve made of brass not plastic.

If the sprinklers run for several minutes, that must be more than 2 gallons from your tank. So, is the well maybe just not giving the water you need. Tell us about the well. Size, depth to water etc.

bob...