Air leak.

Put a ziplock bag around the tube to catch the springs, grip the cap through the bag and pull (pretty hard). It will come off and the springs and balls will be caught in the bag. Upon replacement, I only use one spring and ball and it works fine. Frankly, I think you’re better off with a standard (non gauge) end cap
Thanks will try .
 
yep, just yank it off, its the ball bearings keeping it in place. the plastic bag is a nice tip as there are springs beneath the ball bearings

btw, how did you work out the leak was at the front gauge if you couldn't remove the cap?
yep, just yank it off, its the ball bearings keeping it in place. the plastic bag is a nice tip as there are springs beneath the ball bearings

btw, how did you work out the leak was at the front gauge if you couldn't remove the cap?
Because I had the other one leak a short time ago, I can tell when the gauge spins easily. These teeny o rings flatten out easily I have extras.
When l get this done I have a clean bucket of water to submerge it in to test everything.