Winco DGC-500 - Manual (Page 43)

DGC-500 Functional Description 3-23
NOTE
With Enable ECU Support selected, there is a non-programmable Coolant Level
Sender Fail alarm that can annunciate when the engine is either off or running.
Coolant level is metered and displayed only when Enable ECU Support is
selected in BESTCOMS.
ECU Constraints
An external source cannot always turn the engine off without removing power from the ECU. Removing power
from the ECU is the only way to remove fuel from the engine and shut it down. Different ECU manufacturers
have their own rpm setpoints for reapplying fuel to an engine. For example, if the ECU is powered up and the
engine is still spinning above 60 rpm, the ECU may automatically turn the fuel on.
Not being able to stop the engine without removing power from the ECU causes two problems. The first
problem is that the only way to stop the engine is to turn the ECU off and wait for the engine speed to
decrease below 60 rpm before reapplying ECU operating power. Otherwise, the engine will resume running.
The second problem is that while the ECU is off, you can no longer meter and update coolant level, coolant
temperature, oil pressure, and engine speed values, effectively disabling features like low coolant temperature
alarm/pre-alarm and crank control.
The DGC-500 Solution
The DGC-500 resolves ECU constraints by using four user-programmable timers that are accessed through
BESTCOMS. Each timer setting is described in the following paragraphs.
Pulse Cycle Time. This timer setting establishes the time, in minutes, that the DGC-500 waits before pulsing
the ECU again.
Response Timeout. This timer setting defines the length of time, in seconds, that the DGC-500 attempts
communication with the ECU when the DGC-500 is in the Pulsing state or Connecting state.
Settling Time. This timer setting controls the length of time, in tenths of seconds, that the DGC-500 gathers
data after connecting to the ECU during the Pulsing state. This allows all metered values to be sent and
ramped up to their steady state values. Metered values are sent out by the ECU at different rates as
designated by the J1939 protocol. ECU values initially sent are low and the ECU takes time to average out
its own data values.
Engine Shut Down. This timer setting determines the length of time, in seconds, that the DGC-500 remains
disconnected from the ECU when going from Running to Shutdown before starting the first pulse. This timer
should allow enough time for the engine to slow down so that when the DGC-500 pulses, the ECU will not
restart the engine.
Alarms and Pre-Alarms
If ECU communication is not established during the Connecting state or is lost during the Pre-Start, Cranking,
Resting, Running or Cooling states, then a non-programmable ECU Communications Fail alarm is
annunciated. If the last pulse was unsuccessful (ECU communication was not established), then the ECU
Communications Fail pre-alarm will annunciate. The pre-alarm is checked only after the Pulsing state and is
annunciated only during the Ready state.
To clear Coolant Level alarms when ECU power support is needed, the user must first correct the condition
causing the alarm and then pulse the ECU to update the data. The user may pulse the ECU remotely through
BESTCOMS or locally by pressing the front panel pushbuttons in the ordered sequence of Auto, Off.
Fuel Solenoid Relay
Because there is no external fuel solenoid to connect to, the fuel solenoid relay has been designated to control
ECU operating power. For example, Detroit Diesel's ECU applies fuel to the engine only after engine speed
rises above 60 rpm. The following timers control the fuel solenoid relay when the engine is not running.