Fuel Tube Purging - CNG: Notes

WARNING: This page is about a different car, the 2013 RAM 3500 HD and 2013 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

WARNING

Refer to FUEL DELIVERY, CNG, WARNING .

NOTE:

If required, perform the gasoline system FUEL SYSTEM PRESSURE RELEASE

NOTE:

BEFORE ANY PART OF THE COMPRESSED NATURAL GAS (CNG) FUEL SYSTEM IS OPENED FOR REPAIR, THE SYSTEM MUST BE PURGED OF ALL NATURAL GAS. PURGING OF THE SYSTEM IS RECOMMENDED OUTDOORS OR A WELL VENTILATED AREA.

NOTE:

When purging the system. Not all of the CNG will be evacuated. Care must be taken when purging the CNG system.

Use following procedure if the fuel injector rail is not equipped with a fuel pressure test port.

Fig 1: CNG 1/4 Turn Valve Access Panel

Courtesy of CHRYSLER GROUP, LLC

Open the CNG 1/4 turn valve access panel (2).

Fig 2: 1/4 Turn Valve Positions
Courtesy of CHRYSLER GROUP, LLC
Verify the 1/4 turn valve is in the OPEN position.
Close the CNG cylinder tank manual shut off valves.
NOTE:
When both the gasoline and CNG fuel systems are operating normally and the engine coolant temperature above 18°C, the engine should start in CNG mode. If the engine is not operating in CNG mode, use wiTECH^® to force CNG mode.

NOTE:
If the vehicle is unable to start. Cycle the ignition key multiple times to verify the CNG cylinder tanks are closed.
Start and run engine.
Monitor the pressure drop by the CNG fuel level indicator.
NOTE:
After the engine switches to gasoline mode, verify lower system pressure by monitoring the fuel gauge in the instrument cluster or the CNG tank pressure sensor using wiTECH^® .
Verify that the engine is operating on gasoline.
Monitor the cylinder tank high pressure sensor and the fuel rail sensor by using the wiTech^® .
Turn ignition key to OFF position.
NOTE:
The

LOW SIDE

line needs to be slowly open in order to verify the system does not have a faulty shut-off valve or regulator.
Using care. Loosen the low pressure line at the fuel rail.
Using care. Loosen the high pressure supply line to the fuel pressure regulator.
NOTE:
ALTHOUGH THE FUEL TUBES ARE NOW PURGED OF CNG, THE FUEL CYLINDERS ARE STILL UNDER HIGH-PRESSURE. DO NOT OPEN THE VALVES UNTIL ALL HIGH-PRESSURE COMPONENTS HAVE BEEN RESEALED.

The fuel system must first be purged of natural gas if any of the following components are to be removed or repaired:

Any fuel tube (line) or fuel tube fitting
The fuel injector rail assembly
Any or all fuel injectors
The fuel temperature sensor
The fuel low-pressure sensor
The fuel gauge pressure sensor
The fuel fill receptacle
Any fuel cylinder
Any fuel control valve
The 1/4 turn manual shut-off valve
The fuel filters
The one-way check valves
Pressure regulator
The low-pressure fuel shut-off solenoid
The high-pressure solenoid

NOTE:

One or more Diagnostic Trouble Codes (DTC's) may have been stored in PCM memory due to a possible rough idle condition. A diagnostic scan tool must be used to erase a DTC.