The text between the lines below is from the fourth page of Cat’s Data Sheet for your pump, which is available here:
An integral unloader with built-in by-pass is part of the discharge manifold to
provide system pressure regulation and pump protection. This pump also includes
a fixed chemical injector for chemical application.
Pump should be purged of air before commencing with operation. Liquid must
flow through the pump without discharge restriction to assure full system pressure
Install a pressure gauge close to the manifold head of the pump to assist in setting
system pressure and to periodically monitor system pressure.
Setting and adjusting the unloader pressure must be done with the system turned
on. Start the system with the unloader backed off to the lowest pressure setting
(counterclockwise direction). Squeeze the trigger and read the pressure on the
gauge at the pump. Do not read pressure at the gun or nozzle. If more pressure
is desired, release the trigger, turn adjusting cap one quarter turn in a clockwise
direction. Squeeze the trigger and read the pressure. Repeat this process until the
desired system pressure is reached. Thread locking nut up to adjusting cap and
tighten set screw. All high pressure systems should have a secondary relief valve.
Set secondary relief valve 200-300 psi above the unloader setting.
NOTE: Pressure is not set at the factory.
See an integral unloader on a Cat pump set here (which I do not vouch for):