User manual BENDIX PP-3 TRAILER SUPPLY VALVE

[. . . ] In normal use the button is pulled out before uncoupling from the trailer and pushed in after coupling to the trailer. Should a condition occur resulting in air loss from the tractor or trailer system through leakage and the driver fails to manually pull out the PP-3TM valve button, the PP-3TM valve will automatically close at approximately 40 psi and seal the tractor air lines. The driver cannot, in this condition, overcome the emergency application of the trailer brakes by holding the PP-3TM valve button in. If the driver should hold the button in as emergency line pressure bleeds down from the 40 psi range to approximately 30 psi, the tripper piston will move and open the tripper exhaust in the PP-3TM valve. [. . . ] Delivery line from PP-3TM valve delivery port is connected to tractor emergency port of TP-3TM valve. PP-3TM valve exhaust port and tripper exhaust must be open. Two (2) ports marked "Del" on upper PP-3TM control valve body are plugged and must remain plugged. OPERATING AND LEAKAGE CHECKS To make the following operating and leakage checks, an accurate test gauge installed in a spare hose coupling is required. The vehicle dash gauge should be checked for accuracy against the test gauge prior to making these tests. Block and/or hold the vehicle by a means other than air brakes during these tests. Drain vehicle reservoir supply, then close drain cocks. Connect assembled hose coupling and test gauge in tractor emergency hose coupling. Start engine and build up system pressure. As reservoir pressure builds up there should be no pressure reading on test gauge. When system pressure reaches the 30 to 40 psi range on dash gauge make and hold a foot or hand valve application and observe 2 DISASSEMBLY PP-3 PUSH-PULL VALVE 1. Button pin (1) Figure 3, button (2) and mounting nut (3) are normally removed when valve is removed from vehicle. Remove two lower body cap screws (4) and lock washers, then lower body (5) with cover (6). Remove cover with tripper piston (7) from lower body. Remove tripper piston and spring (8) from cover. Remove tripper piston and cover seal o-rings (9 & 10). Insert rod or punch in upper plunger pin hole and hold plunger (11) from turning while inlet and exhaust valve nut is removed. Remove plunger spring (15) and o-ring (16). Do not remove plugs from ports marked "Del" in upper body. CLEANING AND INSPECTION OF PARTS Wash all metal parts in mineral spirits and then dry. In particular, make sure supply port in PP-3TM valve upper body, tripper by-pass slot, and tripper exhaust port in cover are thoroughly cleaned and unrestricted. Inspect all parts for excessive wear or deterioration. TM Inspect seats in upper and lower body for nicks and burrs. Inspect plunger and tripper piston bores in bodies and cover for deep scratches or nicks. [. . . ] Never exceed manufacturer's recommended pressures. 7. Never connect or disconnect a hose or line containing pressure; it may whip. Never remove a component or plug unless you are certain all system pressure has been depleted. Use only genuine Bendix ® replacement parts, components and kits. [. . . ]