Brake Fluid Pump: Description and Operation

CONSTRUCTION
The power unit consists of a motor and a plunger-type pump. This unit transmits the revolution of the motor to the plunger by way of an eccentric bearing and supplies high-pressure brake fluid to the accumulator by the effect of the reciprocating movement of the plunger.

OPERATION
When the pressure in the accumulator drops below the prescribed pressure level, the pressure switch gives an OFF-signal. The ABS control unit turns the motor relay ON to start the operation of the pump upon the reception of this signal and a signal from the wheel sensor that the vehicle is running at a speed greater than 6 mph (10 km/h). When the pressure in the accumulator attains the prescribed pressure, the ABS control unit turns the motor relay OFF approximately three seconds after the unit receives an ON-signal from the pressure switch. By this, the high-pressure in the accumulator is maintained.

PURPOSE
The ABS control unit turns the pump off and lights the system indicator light if the accumulator pressure does not reach the prescribed level after the pump has run continuously for 120 seconds.