well pump looses pressure

I just replaced my flotec 3/4hp shallow pump with a craftsman 3/4hp hydroglass pump. The old pump worked perfect until it puked. With the new sears pump it has a 40-60 switch, pumps up to 60 no problem, turn on 1 sprinkler and the pressure drops to 40 psi and pump turns on, after a minute the pressure drops to 15-20 psi. The bladder tank is set at 40psi ( per instruction manual ) and holding and if you open 2 spikets at one time the pressure drops to nothing. As soon as you shut off the spikets it builds up pressure to 60 psi and holds. When the sprinkler is on you can here air spurting from it. The old flotec never had this problem. Anybody know if sears has a problem with there pumps? I did not move anything on the suction line and does not seam to leak down as if there was a leak on the suction line. I have looked at everything ( I think ) and can not find where it is pulling air or why the pressure drop. Please help.... I personnaly think it is the pump.

Thanks, Jon

 

Usually, if a pump will reach it's cutout pressure, 60 psi in this case, there's nothing wrong with the pump itself. It sounds to me like the pump is pulling air from somewhere. If there are no leaks on the suction line, the pump casing, etc., then I'd surmise that the footvalve isn't submerged enough. Check that out first.
Just curious here though - What happen to the other pump that suddenly cause it to "puke"?
Ron