Automotive Systems

Formerly Automotive Systems I

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Celect System

Celect System

The Celect 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:

    1. Engine torque and horsepower curves
    2. AFC (air-fuel control) to limit exhaust smoke
    3. Engine low idle and high speeds
    4. Functions as a vehicle road speed governor
    5. Optional vehicle/engine cruise control
    6. PTO (power takeoff) operation
    7. Idle shutdown, 3 to 60 seconds
    8. Gear down protection

For the Celect system to operate, major components are required. These components are as follows:

  1. The 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 operating temperature.
  2. The 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 time.
  3. The 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.
  4. The oil pressure sensor (OPS) is used by the ECM to monitor engine oil pressure during operation.
  5. The coolant temperature sensor (CTS) is used to monitor the temperature of the engine coolant.
  6. The coolant level sensor (CLS) is used to tell the ECM of a coolant level loss.
  7. The ambient air pressure sensor (APS) is used by the ECM to determine the basic operating altitude of the vehicle.
  8. The intake manifold temperature sensor (IMTS) allows the ECM to determine air temperature and adjust fuel rate accordingly.
  9. The 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 asking for.
  10. The 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.
  11. output 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 horsepower produced.

Two other 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:

  • A 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.
  • A 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:

  • The 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.
  • The cruise control panel has two toggle switches—one 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.
  • The engine brake panel has two toggle switches—one 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 compression braking.

On the right-hand side of the control panel are two warning lights—one 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.

Published by SweetHaven Publishing Services
Based upon a text provided by the U.S. Navy

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