system is a full electronic controlled injection and governing system. The major reason
behind the adoption of electronic fuel injection control is to be able to meet not only
the EPA (Environmental Protection Agency) exhaust emission controls but also ensure
optimum fuel economy. This is done by constantly monitoring major engine operating
parameters that have a direct bearing on engine combustion efficiency. A number of engine-
and vehicle-mounted sensors are used to update timing and metering values continually. The
Celect system controls the following major operating factors:
torque and horsepower curves
(air-fuel control) to limit exhaust smoke
low idle and high speeds
as a vehicle road speed governor
vehicle/engine cruise control
(power takeoff) operation
shutdown, 3 to 60 seconds
For the Celect
system to operate, major components are required. These components are as follows:
electronic control module (ECM) contains the hardware required to activate the ECI system.
Within the ECM are such controls as the EPROM (electrically erasable programmable
read-only memory), CPU (central processing unit), RAM (random access memory), and also
contain in the ECM is the A/D (analog/digital) converter. The ECM sends electrical signals
to the injectors, engine brake solenoids, the fuel shutoff valve, and other optional
items. The ECM is mounted to a cooling plate which has diesel fuel continually routed
through it from the pump in order to keep the internal solid-state components at a safe
engine position sensor (EPS) is required to tell the ECM where the various pistons are and
what stroke they are on, so the correct injector solenoid can be activated at the right
oil temperature sensor (OTS) is used to advise the ECM of the oil temperature. The signal
is used by the ECM to determine the engine idle speed at start-up as well as reducing the
fueling rate any time the oil temperature rises to an undesirable level.
oil pressure sensor (OPS) is used by the ECM to monitor engine oil pressure during
coolant temperature sensor (CTS) is used to monitor the temperature of the engine coolant.
coolant level sensor (CLS) is used to tell the ECM of a coolant level loss.
ambient air pressure sensor (APS) is used by the ECM to determine the basic operating
altitude of the vehicle.
intake manifold temperature sensor (IMTS) allows the ECM to determine air temperature and
adjust fuel rate accordingly.
throttle position sensor (TPS) is basically a potentiometer or variable resistor
arrangement that is designed to a output voltage signal to the ECM, based on the degree of
the throttle pedal depression. The ECM is able to determine how much fuel the operator is
vehicle speed sensor (VSS) is required to tell the ECM the road speed of the vehicle. The
VSS sensor is mounted into the transmission 11.
shaft housing in order to monitor the output shaft speed. The electronically controlled
injectors receive low-pressure fuel from a simple engine-driven gear pump. Each injector
is mechanically operated; however, timing and duration of injection is controlled
electronically by a signal from the ECM. This signal is referred to as
pulse-width-modulated (PWM). The longer the PWM signal is, the longer the injector will
deliver fuel to the combustion chamber. The greater the fuel delivery, the greater the
major control switches are required with the Celect-ECI system in order to control the
cruise control, the PTO (power takeoff), and the engine compression brake:
clutch switch is used to allow cruise control or engine brake activation. It is mounted so
that when the clutch pedal is pushed down (clutch disengaged), the clutch switch opens the
switch and deactivates the engine brake or PTO.
brake switch is located in the service air line and will remain in the closed position any
time the brakes are released. Applying the brakes will cause the brake switch to open and
break the electrical circuit to both the cruise control and PTO systems.
In addition to
the engine-mounted components, there are several cab-mounted controls arranged on a small
control panel that can be activated by the operator through a series of small toggle-type
switches. This control panel contains the following:
idle-speed adjustment switch is used to adjust the engine idle speed between 550 and 800
rpm. Each time the switch is moved briefly to the + or position, the idle speed
will change by approximately 25 rpm.
cruise control panel has two toggle switchesone is a simple ON/OFF switch and the
other is the actual cruise control position select switch that the operator uses to set
and adjust the cruise control speed during operation.
engine brake panel has two toggle switchesone switch has an ON/OFF position to
activate either a Jacobs or Cummins "C" brake system and the other switch, used
with the engine brake control, can be placed into position 1, 2, or 3. In position 1 the
compression brake is activated only on two cylinders; position 2 will activate the
compression brake on four cylinders; position 3 will allow all six cylinders to provide
the right-hand side of the control panel are two warning lightsone yellow, the other
one red. The yellow light is labeled warning, while the red light is labeled stop. When
the yellow light comes on during engine operation, this indicates that a Celect system
problem has been detected and recorded in the ECM memory. The problem is not serious
enough to shut down the engine, but should be checked out at the earliest opportunity. If
the red light comes on, the operator should immediately bring the vehicle to a stop and
shut off the engine.