What is an ABS motor pump?

ABS stands for Anti-lock Brake System. An ABS motor pump is the device under the hood that pressurizes the brake fluid for use in ABS stops (a stop in which wheel spin has been detected and the computer takes over the braking) and for use in regular stops, in some cars. Power brake systems in cars usually use what's called a vacuum booster to increase the amount of brake pedal force being applied to the master cylinder. This helps people stop a 3000 pound car without having to literally stand with all your mite on a brake pedal. With the advent of anti-lock brakes, manufacturers realized they could use a motor to pump up the brake fluid pressure internally and do away with the brake booster, even for normal stops. It depends on the manufacturer of the car, what the exact job of the ABS motor is. But, for every manufacturer that uses an ABS motor pump, it is always used during ABS stops to increase internal brake fluid pressures.