HPA Hand Pump - constant downward pull

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sticman77

sticman77

Member
Jul 31, 2019
636
26
ID, United States
i thought i had finally fixed my pump by replacing the o rings on the small piston (they were deformed from overheating). that alleviated the air not being able to move out of the pump.



I am still having issues where the pump seems to suction/pull the handle downward after an up stroke. Is anyone aware of what seal I need to replace for this? I didn't see any other o-rings that looked deformed in my dissasembly.
 
I used to have the same problem with a Benjamin pump. Watch this

http://www.youtube.com/watch?v=BXt4Z7UulKA 

Pay particular attention to the video at 4:15

And then again at 23:20

The brass piece he is screwing on the lower brass piece has a black C clamp across the top of it. Take the C clamp off and you will find a small round ball inside that is made of rubber. It very often times gets covered in grease and can cause it to stick in place blocking the flow of air.

Hope this helps

Shalom

John
 
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