I am having the same problem with my new Procon pump. The outgoing pressure builds up and it does not allow the presoak to work. This is getting annoying!
Well I had the same problem today. The presoak did not work and the pressure built up on the outgoing side of the check valve so the check valve could not open. This time I called Greg for a little help. I adjusted the air regulators (there are 2 air regulators one for the sides and one for the top). I let the unit pump presoak for about 15 minutes and ran the gantry back and forth down the track to try and replicate the problem. Greg believes that there is a kink in the presoak hose somewhere in the system.
The Procom pump is running at 75 psi and the pressure at the gantry is 50 psi, the air is set at 35 psi.
I got my temporary Procon pump from my Dad today. I have never replaced a Procon pump but William said it is easy, which it was.
You just have to remove the old pump. Mine is a clamp style because it is clamped on like the second picture shows. The other type is flange type.
Then you put the “magic piece” (second picture) which make everthing work in the motor, line it up with the pump, tighten the clamp on the pump and motor, install all the hoses back correctly and test. Done!