COUPLING 7M9533 - Caterpillar

3500 Series Industrial, Marine And Vehicular Engines Using A 3161 Governor Equipped With Pneumatic Speed ControlIncorrectly adjusted pneumatic speed controls, or incorrectly adjusted system (signal) air pressure can cause unexplained speed changes or an inability to reach high or low idle. Before attempting any adjustment of the pneumatic speed control, the pressure of the air signal from the remote throttle should be monitored and corrected to insure that the correct pressures are being supplied. This can be done by installing the parts listed in the chart on the governor as shown in the illustration.
Pneumatic speed setting control.The signal air pressure range should be 35 kPa (5 psi) below the pressure at which the governor reaches low idle and 35 kPa (5 psi) above the pressure at which the governor reaches high idle. For example, if the governor's pneumatic control is factory set to reach low idle at 34.5 kPa (5 psi), the signal pressure at the minimum throttle setting should not exceed 0 kPa (0 psi). If the governor's pneumatic control is factory set to reach high idle at 365 kPa (52.9 psi), the signal pressure at the maximum throttle setting should be 400 kPa (57.9 psi) or 35 kPa (5 psi) more.
When the pressure signal from the remote throttle has been found to be correct, the pneumatic speed control on the governor can be adjusted according to the 3161 Governor Service Manual (SENR3028).
To confirm that the signal air pressure is moving the governor to high and to low idle, the governor face plate can be removed. You can now see if the speed setting shaft lever makes contact with both the low speed and high speed stop screws.
If the speed setting shaft lever does not contact the low speed stop screw (no signal air pressure to the pneumatic control), the engine speed will not drop when the low idle screw is backed out. Before doing the governor pneumatic speed control adjustment procedure in the service manual, turn the speed level adjustment screw (on governor pneumatic speed control) until the speed setting shaft lever contacts the low idle screw.