FIRE TRUCK PRESSURE GOVERNOR FAULT
2. Turn ON pump control switch.
3. Verify all interlocks are set (parking brake, transmission neutral, etc.)
4. Plug in DDR. Select Switch/Light status.
5. Observe the displays and Set/Coast, while depressing the decrease switch.
[a] If DDR displays OFF to ON when Set/Coast decrease is depressed, check the EFC.
Refer to section 10.13.9.
[b] If the DDR displays OFF when decrease is depressed, circuit #541 is open or shorted
to a voltage source. Repair the fault and retest.
10.13.9 Electronic Fire Commander
The Detroit Diesel Electronic Fire Command (EFC) is designed to support Detroit Diesel
engines in the fire fighting market. It combines a Pressure Sensor Governor (PSG) controller, a
system monitor, and a display for vital engine operating parameters into one compact, durable
package. It also provides complete control and monitoring of the DDEC engine control system on
a fire truck when pumping.
Pressure Sensor Governor Operating Modes
The EFC commands the Detroit Diesel PSG system to operate in one of two modes. 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 operating
mode of the PSG can be changed from RPM Mode to Pressure Mode and back by pressing the
MODE button. When the unit is first turned on, the RPM Mode is active. Pressing MODE switch
engages the Pressure Mode and another press brings the system back to RPM Mode. The PSG
system utilizes the engine speed or pump pressure that is current at the time the button is pressed.
In the Pressure Mode, the PSG system operates like cruise control for the water pump pressure,
and maintains the pressure at a chosen setting. Engine speed is constantly adjusted to maintain the
desired pump discharge pressure. 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).
The RPM Mode keeps the engine speed constant even when the load varies within the engine's
operating capability. The pump output pressure may vary in this mode, but the engine speed does
not. The driver/engineer uses the EFC to choose which of these two modes the PSG uses. The
EFC also allows the driver/engineer to finely adjust the pressure setting or the engine speed
setting to match prevailing conditions.
Setting the Revolutions Per Minute Mode
Perform the following steps to set the RPM Mode:
1. Start engine and ensure the EFC is ON.
2. Ensure the conditions are met for the Throttle Ready lamp to be ON. (These are usually
interlocks necessary to allow increased throttle operation.)
All information subject to change without notice.
6SE497 9709 Copyright © 1997 DETROIT DIESEL CORPORATION