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Fuel Delivery, CNG: Description: Description-CNG

WARNING: This page is about a different car, the 2012 RAM Pickup and 2012 RAM Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:

WARNING 

Refer to WARNING .

Fig 1: CNG Fuel System
GC0155480Courtesy of CHRYSLER GROUP, LLC

The Compressed Natural Gas (CNG) fuel system is equipped with the 5.7 liter engine.

The CNG vehicle still utilizes gasoline. The engine operates using gasoline when the temperature is below 18°C (64.4°F) before switching to CNG. The engine will switch back to gasoline when the CNG system falls below the low fuel threshold.

CNG is in the cylinder tanks (4) and is always under high pressure even when the vehicle is at rest. With the CNG fuel system under extreme pressure, the use of a fuel pump is not required in the CNG system.

The Ram 2500 CNG engine starts and runs on CNG for all starts, when the engine coolant temperature is at or above 18°C (64.4°F). To make sure the gasoline does not get stale, the PCM uses a "Minimum Gasoline Consumption" feature. This feature will consume one tank of gasoline about every 8000 miles regardless of tank size. The routine will force the engine to run on gasoline until a programmed amount of gasoline is used. The routine will never run more than once per ignition cycle.

When the engine coolant temperature is between approximately -18°C (0.0°F) and +18°C (64.4°F), the Ram 2500 CNG will start and run on gasoline until these conditions are meet:

If a gas consumption event is required during a cold-start ignition switch cycle, the amount of gasoline consumed during operation of the Minimum Gasoline Consumption routine will be reduced by the amount of gasoline consumed during the cold start.

When a start occurs with the ambient temperature below approximately -18C (0.0°F), the gasoline consumed after the cold start will exceed the amount required by the Minimum Gasoline Consumption feature. The routine will not run during that key cycle.

However, certain high-load conditions may cause the fuel system to switch from CNG back to gasoline. For example, the system will switch to gasoline operation whenever the driver keeps the engine at wide open throttle for an extended period of time.

Because of the high pressure. A pressure regulator (2) is used to control the CNG entering the fuel rail to a lower consistent pressure.

Additional or unique components used with CNG fuel system include: 

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