There is a check valve in the fuel pump that lets the fuel system retain residual pressure. Typically 15 psi or so. If a pressure regulator sticks on the high pressure side it slams the check valve with a higher than normal pressure. This eventually causes the valve to imbed itself into the seat and now the fuel pump has to overcome this excess residual/seated pressure which causes the pump to draw excessive amperage. If i see a bad fuel pressure regulator i always inform the owner that their fuel pump is probably short for the war. The most common cause of a bad regulator is fuel contamination. Water etc.