The invention relates to a liquid pump comprising: a cylinder (2); a valve (4) for taking liquid into the cylinder; a valve (5) for discharging the liquid out of the cylinder; a piston (2) sliding in said cylinder so as to draw the liquid into the cylinder and to expel the liquid out of the cylinder; a cylinder-heating electric circuit (7) with at least one resistor (70, 71) for electrically heating the liquid in the cylinder; a temperature sensor (11) for measuring the liquid temperature in the cylinder; and a control circuit (8) for reducing the electric current in said heating electric circuit and for starting the discharge of the liquid out of the cylinder as soon as the liquid temperature has reached a predetermined setpoint value.
