Problem with NEMA 17 17HS3401

Hello, I'm new in the world of 3d printers, this week I try to make a Prusa iteration 3. When I was trying to make the motors move, I saw there is something wrong, the motors (NEMA 17 17HS3401) not functioning properly, I mean, I turn on the power (12V and 40A), and whit the pronterface I can make the motors move, but when I mount the motor in the axis they do not have enough strength to move any axis.
I try to increase the amperage in the pololu (300 mA) and nothing happens. When I'm increasing the flow, reaches a point where it was 350 mA and this "jump" to 1A. I dont know if the problem is in the source or somewhere else. If anyone can help I would be very grateful, thank you very much and sorry for my bad english

Additional Information

RAMPS 1.4
Arduino mega 2560
Pololu 8825
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Step Motor 17HS3401
Step angle 1.8°
Rated Current 1.3 A
Holding Torque 28

When the pot on the stepper driver is adjusted, it changes the voltage Vref. The current is calculated for each Vref, by a formula that is on the driver ic datasheet or in this case also on pololu website.
The potentiometer on the stepper driver pcb is in a voltage divider, e.g. it changes the voltage continiously and normally it cannot "jump". If it "jumps" it may be because its a carbon track pot, and its carbon track may be damaged, which means it needs replacing.

ok, thanks. I solve the problem changing Sprinter whit Marlin.