how do you turn up the fuel pump on a 12 valve cummins?

Answer 1

That all depends on what pump you have on it. the rotary pump or the in-line.
Rotary turn loosen pump and turn to 1.55mm to 1.65 mm. Break off the tamper proof cover on the top back side of the pump, turn screw in--until rpms are raise 50 rpm, then adjust idle speed back down 50 rpms. remove vent cover and top cover on the fuel pump, loosen top jam nut even with the top of the screw then screw down until nut touches, then tighten nut. last and least turn star wheel to loosen spring force on the "air" setting.
In-line pump--change timing to 15 degrees BTDC (before top dead center), put in a cam kit or a "slider" kit, adjust "air setting" by removing spring tension on star wheel.---many other things you can do--but you limited to the pump.

Answer 2

There are many things that you can do. The cheapest is find the cap on the back of your pump and take it off and turn the screw up.