well. i returned it and got another brand new one, tried it out and the same problem again

i think it may have to do with the newly enlarged chamber and the rate that the air flows through it. since i cant take it back again with the same problem i will open it up and try to see the problem. i think it may be possible that the diaphram has just been lifted too hgh and is not going back dow.
Walrus; it just equalises as i pump in the air, just as if there were no valve at all
Spudshot; i will try that once i have opened it up and checked it.
Walrus again; i dont think this is the problem as i pumped slowly and when i has a smaller chamber it all went fine.
i guess i have to make the chamber smaller no matter what

thanks guys.
---Julz