Fuel Actuator
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| Illustration 1 | g03660013 |
Location of the fuel actuator (left side top engine view) (1) Fuel actuator | |
Fuel actuator (1) is electronically controlled and electrically actuated. The fuel actuator and the ECM communicate via the CAN data link.
Throttle Actuator
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| Illustration 2 | g03660018 |
Location of the throttle actuator (right side top engine view) (2) Throttle actuator | |
Throttle actuator (2) is electronically controlled and electrically actuated. The ECM issues commands to the actuator via the CAN data link.
Electronic System
The Cat Electronic System is a complete electronic control system for gas engines. The following benefits are the most significant advantages of the electronic system:
- Air/Fuel ratio control
- Extensive system diagnostics
- Elimination of parts that are prone to mechanical wear
- Precise control of engine operation
- Engine protection
- Timing control of individual cylinders
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| Illustration 3 | g03659492 |
Electronic Control Module (ECM) | |
Most of the functions of the electronic system are provided by the Electronic Control Module (ECM).
Five primary functions are supported by the ECM:
- Governing of the engine rpm
- Control of ignition
- Control of the air/fuel ratio
- Start/stop control
- Monitoring of engine operation
Governing of the Engine RPM
The ECM maintains the desired engine speed through electrical control of the throttle. The throttle regulates the throttle plate.
For more information on the desired speed input, see the Systems Operation/Testing and Adjusting manual.
Control of Ignition
An ignition harness connects each transformer to the ECM. The harness is routed outside the engine.
Control of Air and Fuel
The ECM determines the desired volume for the flow rates of the air and fuel. The ECM sends information on the desired flow of air and fuel to the fuel metering valve. The ECM fine tunes the signal to the fuel metering valve in order to achieve the desired emissions. The process is repeated continuously during engine operation.
Start/Stop Control
The ECM contains the logic and the outputs for controlling the starting and stopping of the engine. The logic for starting and stopping can be programmed by the customer.
The engine uses an energize-to-run system. The gas shutoff valve must remain energized in order to supply fuel to the engine. If power is removed from the gas shutoff valve, the fuel is shut off.
Monitoring Engine Operation
Sensors are used in order to monitor engine operation. Wiring harnesses connect the sensors to the ECM. The ECM uses information from the sensors in order to monitor the engine. The ECM also uses information from the sensors in order to control the engine. The information is also used to generate event codes, and diagnostic codes.
Note: The codes can be read with Cat Electronic Technician (ET). The codes can also be read on the panel.
Event - An event is a result of abnormal engine operation. If abnormal engine operation is detected, the ECM generates an event code. The ECM can generate an alarm or a shutdown for abnormal engine operation. These conditions are some examples of events: high inlet air temperature, low oil pressure and engine overspeed.
Diagnostic - A diagnostic code is a result of a problem with the operating system or with the monitoring system. The ECM uses sensors and internal circuitry to monitor the system components. If a problem develops in a component or a wiring harness, the control system will sense the problem. The control system will notify the operator by creating a diagnostic code. Some examples of conditions that activate diagnostics are a short in a circuit for a sensor, an open circuit, or a noisy signal.
Note: For detailed information on event codes and diagnostic codes, refer to Troubleshooting.
Sensors
Sensors provide information to the ECM. The information enables the ECM to control the engine as efficiently as possible over a wide range of operating conditions. The information is used for monitoring engine operation and for engine protection.
Illustrations 4, and 5 show the locations of the sensors.
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| Illustration 4 | g03648155 |
(3) Engine coolant temperature sensor (4) Intake manifold air temperature sensor (5) Intake manifold air pressure sensor (6) Engine oil temperature sensor | |
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| Illustration 5 | g03646402 |
(7) Speed/timing sensor (8) Oxygen sensor (9) Oxygen buffer (10) Oil pressure sensor (11) Panel for the circuit breakers | |
The functions of the sensors are described below.
Engine coolant temperature sensor (3) - The temperature sensor is located in the water temperature regulator housing. To monitor the coolant temperature, the element must be in contact with the coolant. If overheating occurs due to low coolant level, the sensor will not function properly. A high coolant temperature will activate an alarm, a derating, or a shutdown. A low coolant temperature will only activate an alarm. The setpoints for the activation can be programmed with the ET. The engine can be restarted after a shutdown due to high engine coolant temperature. However, another shutdown will occur after 1 minute if the temperature remains high.
Intake manifold air temperature sensor (4) - An intake manifold air temperature sensor that is producing an incorrect signal will have an adverse effect on the air/fuel ratio.
Intake manifold air pressure sensor (5) - An intake manifold pressure sensor that is producing an incorrect signal will have an adverse effect on the air/fuel ratio.
Engine oil temperature sensor (6) - An oil temperature sensor monitors the engine oil temperature. A high oil temperature will activate an alarm or a shutdown. The ECM compares the oil temperature to the engine coolant temperature. A high difference between the two temperatures will activate an alarm or a shutdown.
Speed/timing sensor (7) - The engine speed/timing sensor is located on the rear end of the left camshaft. The engine speed/timing sensor provides accurate information about the position of the crankshaft and the engine rpm to the ECM. The ECM uses the position of the crankshaft in order to determine ignition timing.
Oxygen sensor (8) and oxygen buffer (9) - The oxygen sensor and the oxygen buffer generate a signal that is proportional to the percent of oxygen in the exhaust. The signal is used for adjusting the air/fuel ratio in order to achieve the level of emissions that is desired.
Messenger display (10) - The messenger display is located on the control panel.
Oil pressure sensor (11) - An alarm or a shutdown can be activated by any of the following occurrences: low filtered oil pressure, low oil filter differential pressure and high oil filter differential pressure.
Sensors for the Catalytic Converter/Muffler
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| Illustration 6 | g01938513 |
Locations of the sensors that are for the catalytic converter/muffler (20) Temperature sensor for the inlet of the catalytic converter/muffler (21) Temperature sensor for the outlet of the catalytic converter/muffler (22) Oxygen sensor for the outlet of the catalyst | |
Circuit Breaker Panel
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| Illustration 7 | g01938594 |
Locations of the circuit breakers that are at the circuit breaker panel (23) Circuit breaker for the ECM (15 amp) (24) Circuit breaker for the auxiliary circuit (20 amp) (25) Circuit breaker for the starting system (40 amp) (26) Circuit breaker for the alternator (40 amp) | |