The driver/engineer uses the EFC to choose which of these two modes the PSG uses. The pump output pressure may vary in this mode, but the engine speed does not. The RPM Mode keeps the engine speed constant even when the load varies within the engine's operating capability. A pressure sensor in the output side of the fire pump is used to measure and feed this pressure back to the DDEC Electronic Control Module (ECM).
Engine speed is constantly adjusted to maintain the desired pump discharge pressure. In the Pressure Mode, the PSG system operates like cruise control for the water pump pressure, and maintains the pressure at a chosen setting. The PSG system utilizes the engine speed or pump pressure that is current at the time the button is pressed. Pressing MODE switch engages the Pressure Mode and another press brings the system back to RPM Mode. When the unit is first turned on, the RPM Mode is active. The operating mode of the PSG can be changed from RPM Mode to Pressure Mode and back by pressing the MODE button. The RPM Mode controls the engine speed to a constant number of revolutions per minute, and the Pressure Mode varies the engine speed to maintain a constant pump discharge pressure. The EFC commands the Detroit Diesel PSG system to operate in one of two modes. It also provides complete control and monitoring of the DDEC engine control system on a fire truck when pumping. It combines a Pressure Sensor Governor (PSG) controller, a system monitor, and a display for vital engine operating parameters into one compact, durable package. The Detroit Diesel Electronic Fire Command ™ (EFC) is designed to support Detroit Diesel engines in the fire fighting market. If the DDR displays OFF when decrease is depressed, circuit #541 is open or shorted to a voltage source.Refer to "10.13.9 Electronic Fire Commander If DDR displays OFF to ON when Set/Coast decrease is depressed, check the EFC.Observe the displays and Set/Coast, while depressing the decrease switch.Verify all interlocks are set (parking brake, transmission neutral, etc.).If the DDR displays OFF when increase is depressed, circuit #541 is open or shorted to a voltage source.If DDR displays OFF to ON when increase is depressed, check the EFC.Observe the displays and Res/Accel, while depressing the increase switch.Pressure Transducer and Harness Connector If the EFC tests okay, refer to "10.13.9 Electronic Fire Commanderįigure 1. If the DDR displays OFF when Pressure Mode is selected, the mode selector wire (circuit #523) or switch is open or shorted to a voltage source."Pressure Transducer and Harness Connector " Check for possible intermittent open circuitor short to voltage source. If DDR displays ON when Pressure Mode is selected, the mode selector (circuit #523) is functioning properly.If the wiring is incorrect, correct the wiring and retest.If the EFC tests okay, refer to "10.13.6 Verify Mode Selector Operation" If the wiring is correct, refer to "10.13.9 Electronic Fire Commander.Compare pressure sensor harness wiring to the diagram.Perform the following steps to identify the problem:
Manual, 7SA800 and refer to "10.13.10.3 Troubleshooting the Electronic Fire Commander" Refer to the DDEC III Application And Installation
DETROIT DIESEL ELECTRONIC FIRE COMMANDER 23519655 MANUAL
Refer to the Application and Installation manual for the appropriate engine model to ensure correct inputs and outputs are configured. Perform the following steps to verify the PSG configuration. Verify Correct Pressure Sensor Governor Configuration The Pressure Sensor Governor (PSG) System is a DDEC feature, programmed to allow the engine speed to change in order to maintain a steady water pump pressure (pressure mode) or hold a steady engine speed (RPM Mode).
The following procedure will troubleshoot fire truck pressure governor fault. Section 10.13.1
0 kommentar(er)
