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Rick, I fail to understand what service manual says the relief should open a 2-5 psi, The normal operating pressure is around 4-5 psi, so it wouldn’t be able to come up to normal if the relief was opening at less than 5.
Let’s back off and reconsider. Under normal operation, the relief valve will never open. The pressure in the tank builds to the maximum crankcase pressure pulses in the motor, normally around 4-5 psi. So it is the motor that controls the maximum tank pressure under normal conditions.
The other factor to consider is heat, like from sitting out in the hot sun. That can cause a significant pressure increase. and that is what the relief valve is for. It will open and bleed off excess pressure before the tank blows up. I would have to do some research to find out what the relief valve setting is, but it certainly is higher than what the motor normally pumps in. I’m guessing around 8-10 psi, but that is a guess. I’ll see if I can find the real number.