An industrial pneumatic pump for a viscous fluid comprising: - a pump body; - a double-acting pneumatic cylinder comprising an external liner, a piston, a first chamber and a second chamber separated by said piston; - a pump shaft integral with said piston and sliding in a channel; - a pressure chamber arranged along said channel and provided with an inlet port for compressed air and an outlet port for said air; - a suction mouth for said viscous fluid; - an outlet mouth for said viscous fluid; - a connection chamber connected to said first and second chambers by means of a first and a second duct and corresponding access holes (36, 37), respectively, and to said channel in which said pump shaft slides by means of said outlet port, and provided with a hole for discharging air into the atmosphere; - a distributor comprising a spool adapted to put said first chamber and said second chamber in communication respectively and alternatively with an air discharge hole to the atmosphere and with said an outlet port of said air, implementing a reversal system for said double-acting pneumatic cylinder; - a first and a second pneumatic pistons acting opposite each other on said spool to move it in said connection chamber, sliding respectively in a first and a second service chamber connected to said channel in which said pump shaft slides by means of ports (32, 33); - a base for fixing said pump body to a dip tube in which said suction mouth is formed, characterized in that said spool sliding in said connection chamber due to the effect of said pneumatic pistons (22, 23) opens or closes the access holes (36, 37) of said first and second duct alternatively, putting the respective chambers (6, 7) of said pneumatic cylinder under pressure or discharging them, characterized in that said spool comprises a thickening adapted to cooperate with said air outlet port from said pressure chamber to modulate the entry of air into said connection chamber and cause a pressure perturbation in the service chambers (24, 25) of said first and second pneumatic piston, causing the immediate displacement of the piston (22, 23) called to act on the spool. - a pump body; - a double-acting pneumatic cylinder comprising an external liner, a piston, a first chamber and a second chamber separated by said piston; - a pump shaft integral with said piston and sliding in a channel; - a pressure chamber arranged along said channel and provided with an inlet port for compressed air and an outlet port for said air; - a suction mouth for said viscous fluid; - an outlet mouth for said viscous fluid; - a connection chamber connected to said first and second chambers by means of a first and a second duct and corresponding access holes (36, 37), respectively, and to said channel in which said pump shaft slides by means of said outlet port, and provided with a hole for discharging air into the atmosphere; - a distributor comprising a spool adapted to put said first chamber and said second chamber in communication respectively and alternatively with an air discharge hole to the atmosphere and with said an outlet port of said air, implementing a reversal system for said double-acting pneumatic cylinder; - a first and a second pneumatic pistons acting opposite each other on said spool to move it in said connection chamber, sliding respectively in a first and a second service chamber connected to said channel in which said pump shaft slides by means of ports (32, 33); - a base for fixing said pump body to a dip tube in which said suction mouth is formed, characterized in that said spool sliding in said connection chamber due to the effect of said pneumatic pistons (22, 23) opens or closes the access holes (36, 37) of said first and second duct alternatively, putting the respective chambers (6, 7) of said pneumatic cylinder under pressure or discharging them, characterized in that said spool comprises a thickening adapted to cooperate with said air outlet port from said pressure chamber to modulate the entry of air into said connection chamber and cause a pressure perturbation in the service chambers (24, 25) of said first and second pneumatic piston, causing the immediate displacement of the piston (22, 23) called to act on the spool.