RE: Weird UP-3 valve problem
Hi.
I have 9 of these valves so I can tell you I have a ton of experience with them.
First your UP valves are covered for life by Ultra Precision. It does not matter if a part fails from wear or if you damage the valve in a crash. You simply send it back and it is fixed free of charge!! Amazing. I have done this several times.
Next the leaks are usually caused by blow by in one of the gear or door cylinders. do the usual checks to determine which one then fix the problem.
However I do believe that these valves have some quirks. I get irregular sequencing or slow to react door at times and I can usually solve the problem by lubing the inner plunger as described above. In other cases I do believe that the valve needs to find its own equilibrium. For example if the air runs totally out of the system and I fill it back up and cycle the gear I get the 1/2 way up gear followed by the hissing air. I have found that If I push the gear up all the way by hand and let the hissing continue then just as the air pressure in the tanks get low the doors will close. Then filling the tanks again resumes 100% normal operation of the gears and doors. It will stay that way too as long as you don't let the system go to zero pressure again.
Hope this helps,
Dom