Boiler pressure problem

[Joehsr]

I have a Burnham Boiler K807BW with the following:
Honeywell low water cutoff RW700A
Honeywell outdoor reset T475A1008
Honeywell operating control L4006A
Honeywell Temp limit control with manual reset L4006E
Honeywell high press limit control L404C
Gordon-Piatt Sub-control #180098 ( 3”alarm, Alarm light onn flame failure. High amb Temp, high limit, high water pressure)
Portable expansion valve (vent right VR60)
Here is the problem: I came into a leaking expansion valve. I shut down the water supply and change the expansion valve and set the precharge at 12 psi. Now whenever the boiler start the pressure will rise to 35 psi and shut down the boiler triggering the alarm light. Operating temp 160deg. boiler will not relight unless I reset the pressuretrol!

 

[Reach4]

What is the water pressure you see when cold? You would want the precharge to be as high as the lowest water pressure you see or a little higher. What is the water pressure after the 35 PSI, shutdown, and then the water cools completely?

Pressure tank may have a problem, but it is not totally waterlogged. At the lowest pressure, it should be empty of water.