Well Ive replaced all the o-rings now, apart from in the solenoid, although this did not help. Originally I though it had but it just slowed the leak enough for me to hear another leak from inside the frame. Which turns out its from the solenoid. My fault finding did not cause the problems they were there since I first gassed up the marker.
When you say it was in full working order when it left you, you said via pm that you have not shot it in a while and that the last person to use it was a team mate a few weeks back but didn't say about any problems. So to me it sounds like it developed a problem here and it was sold without a final test by yourself prior to sale.
