Weird sprinkler valve issue

[Shiwudao]

hi there, need your help again! thank you!

I have two Rain birds’ valves as in the picture, both worked last year. This year when I turned on my timer, I found one weird problem on the one in the pinked circle(A), another one(B) works perfectly.
1)when timer turned on this valve A, I can hear water started to flow through, but the flow is very low thus can't pop up sprinkler heads.
2)I thought it may because the solenoid damaged, so I switched the solenoid with another valve B. The valve B still works perfect, but the same issue for this valve A. So -> should not be a problem on solenoid.
3) I unscrewed the top of the valve A, remove the Diaphragm, clean it, and reinstalled it back. still same issue.
4) and then I loose the screw in the red circle a little bit, I can hear the water go strong enough and it works. And then even I tight the screw back, the water continues to go through
5) And then I used timer to shutoff the valve, it works. However, when I turn it on again, the same issue.
6) if I manually turn solenoid counter clock wise 2 or 3 rounds, the water will be strong enough. But if only turn 1/2 round, the water is very low.

any idea ? thank you!

 

[Shiwudao]

for 2), when I switched solenoid with valve B, I mean together with wires, so there should be no issue on wires.

 

[Sponsor]

 

[Jeff H Young]

Busted pipe underground? that would cause a lack of water to the heads and you would still hear it running . I don't know if you'd see wet spots depending on your yard

 

[Shiwudao]

busted pipe underground? that would cause a lack of water to the heads and you would still hear it running . I dont know if youd see wet spots depending on your yard

Thanks, if this is the case then why it works when I manually turn on ? Because manual turn give more water pressure?

 

[WorthFlorida]

Replace the diaphragm. The neoprene hardens up and it doesn't flex enough.

 

[Shiwudao]

Replace the diaphragm. The neoprene hardens up and it doesn't flex enough.

I replaced the top jar (including diaphragm) and it works now, thanks!