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| Illustration 1 | g06266375 |
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(1) Gas shut off valve
(2) Gas pressure regulator (3) Fuel metering valve (4) Fuel inlet (5) Turbocharger compressor | |
The Electronic Control Module (ECM) provides control of the air/fuel mixture to the engine. The following is a diagram of the fuel system main components. The flow of fuel through a typical fuel system is explained below.
Refer to the Application and Installation Guide, LEBW5336, "Gaseous Fuel Systems" for more information on fuel system specifications and installation.
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| Illustration 2 | g06266389 |
The fuel flows from the main gas supply through a knock-down regulator. A knock-down regulator is a second regulator that is needed when the gas supply pressure is too high for a single regulator to manage.
From knock-down regulator, the fuel flows to the fuel filter. Usually, the fuel filter is a component of the design at the particular site. The customer is responsible for supplying clean, dry fuel to the engine. The fuel filter may be supplied by Caterpillar or by the customer. To prevent particles from entering the engine, a 1 micron filter is recommended. Select a filter that is properly sized for the required gas pressure.
For installation of the fuel filter, the recommended location is close to the engine before the engine gas pressure regulator. Pressure gauges in the gas lines on each side of the fuel filter are recommended to monitor the filter differential pressure. A manual shutoff valve in the gas line before the fuel filter will facilitate servicing of the filter.
The filtered fuel flows to the Gas Shutoff Valve (GSOV). The GSOV may be supplied by Caterpillar or by the customer. The solenoid for the GSOV may be connected to engine wiring harness or to a harness that is supplied by the customer. In either case, the customer may install a switch that can interrupt the circuit.
The control system is configured for a GSOV that is energize-to-run. This statement means that the GSOV must be energized in order for the engine to run. The GSOV may be energized by the customer equipment or by the ECM. When the GSOV is energized, the valve opens and the fuel flows to the engine. When the control system shuts down the engine, the voltage is removed from the solenoid. The valve closes and the fuel is shut off.
The fuel flows through the GSOV to the gas pressure regulator.
The regulator may be supplied by Caterpillar or by the customer.
The required fuel pressure stability is
A regulated pressure of
Less gas pressure may result in reduced power. More gas pressure may result in instability.
The fuel flows to the electronically controlled fuel metering valve . The ECM issues a command signal to the fuel metering valve via the CAN data link. The fuel metering valve regulates the flow of fuel to the engine.
The fuel metering valve controls the volume of fuel that flows to adapter for the air inlet elbow. The inlet air that is necessary for combustion also enters the adapter. The air/fuel mixture enters turbocharger compressor.
The compressed air/fuel mixture flows to the electronically controlled throttle. The ECM issues a command signal to the actuator for the throttle via the CAN data link. The signal is based on the desired engine speed. The throttle controls the volume of the air/fuel mixture that flows through aftercooler.
The temperature of the compressed air/fuel mixture is reduced in the aftercooler resulting in an increased density of the air/fuel mixture, resulting in more efficient combustion.
The air/fuel mixture flows from the aftercooler through air inlet manifold. The manifold distributes the air/fuel mixture through the spark arrestor to the cylinders for combustion.