James,
Harrelson

If you don't find a cylinder leaking as mentioned by Bill Harrelson, the emergency dump valve is the next most likely suspect. I had to replace mine following the first system test as it had a serious leak, resulting in the symptoms you describe.

I haven't looked in the LML archives for a long time but I do remember posting this quite a while back (like maybe 1994 - 5) wherein I also mentioned the brand of High-pressure valve with which I replaced the original (I mention this because I can't remember the brand name - though I do remember that I found it in a catalog associated with Swage-Lok). In fact, I used the same brand for the fuel shut-off valve as well.

I don't know what valves are being supplied in the later kits (mine was a very early 235 kit) but the original units were pretty bad. I've had no subsequent problems since installing the new units.

Good luck with your troubleshooting.

Dan Schaefer
N235SP - flying 13 years and still no new leaks.