Fuel Delivery and Air Induction: Description and Operation

FUEL DELIVERY - CNG

CNG Fuel System
The Compressed Natural Gas (CNG) fuel system, as used with 2002 rear wheel drive vans/wagons, will be equipped with a 5.2L (V-8) engine only.

Certain components have been deleted/added/ changed from the 5.2L engine package to allow for operation on CNG.

Unlike gasoline, a natural gas fuel system is always under pressure even with the engine not running. Because the fuel system is under a constant pressure, a fuel pump is not needed.

The function of the EVAP control system is to prevent the emissions of gasoline vapors from escaping from the fuel tank and venting into the atmosphere. Because the engine is not using gasoline, and the CNG cylinders are sealed to the atmosphere, the EVAP canister and canister purge solenoid are not necessary with the CNG system.

Some internal changes have been made to the 5.2L V-8 engine when equipped with the CNG package. Refer to the Engine section for additional information.

The following fuel system components (as used on CNG vehicle) are identical to components used on the 2002 Rear Wheel Drive Van/Wagon equipped with a 5.2L (8 Cylinder) engine.
- Throttle body
- Accelerator linkage
- Manifold Absolute Pressure (MAP) sensor
- Engine Coolant Temperature (ECT) sensor
- Intake manifold
- Intake Manifold Air Temperature (IAT) sensor
- Throttle Position Sensor (TPS)
- Idle Air Control Motor (IAC)
- Camshaft Position Sensor (CMP)
- Crankshaft Position Sensor (CKP)
- Automatic shut-down (ASD) relay (same relay as gasoline powered engine, but has different functions for CNG operation)
- Oxygen sensors
- Vehicle speed signal from ABS module or RWAL module
- Distributor
- All air conditioning components
- All speed control components
- All overdrive components
- Generator (alternator)
- Park/neutral switch (gear indicator signal/auto. trans. only)
- Brake switch controls

Fig.1 Compressed Natural Gas (CNG) Fuel System Components:

Additional or unique components used with CNG fuel system (Fig. 1) will consist of:
- A unique Powertrain Control Module (PCM) computer
- A CNG high-pressure fuel shut-off solenoid relay (controlled by ASD relay)
- A high-pressure fuel fill receptacle with an internal one-way check valve
- A separate, frame rail mounted one-way check valve
- A fuel filter mounted in the fuel pressure regulator
- Eight 8. unique CNG fuel injectors
- High-pressure, stainless steel seamless fuel tubes (lines)
- Silver plated single-ferrule, compression-type fuel tube (line) fittings (not at all fuel tube connections or components)
- A fuel rail mounted, fuel low-pressure sensor
- A unique fuel rail
- Certain unique wiring harnesses
- Four high-pressure fuel cylinders
- Manual fuel control valves (on each fuel cylinder)
- A manual (mechanically operated) 1/4 turn gas shut-off valve
- A fuel rail mounted, fuel temperature sensor
- A fuel rail mounted, and electrically controlled, low-pressure fuel shut-off solenoid
- Certain unique chassis frame members
- A unique transmission oil dipstick tube
- A fuel pressure regulator warmed by engine coolant
- A fuel pressure regulator mounted, and electrically controlled, high-pressure fuel shut-off solenoid
- A temperature compensated, fuel gauge high- pressure sensor (transducer) used to operate the fuel gauge. Refer to Instrument Panel and Gauges

WARNING:
- BEFORE PERFORMING ANY SERVICE OR REPAIR ON COMPRESSED NATURAL GAS (CNG) EQUIPPED VEHICLES, THE FOLLOWING WARNINGS AND SAFETY PRECAUTIONS MUST BE READ AND FOLLOWED:
- THE CNG SYSTEM SHOULD BE SERVICED ONLY BY QUALIFIED NATURAL GAS VEHICLE TECHNICIANS.
- NATURAL GAS VAPORS AT ATMOSPHERIC PRESSURE ARE LIGHTER THAN AIR AND WILL RISE AND DISPERSE IN OPEN AREAS. IN ENCLOSED AREAS, NATURAL GAS VAPOR MAY COLLECT AND FORM A COMBUSTIBLE MIXTURE. IF THE VEHICLE IS ROUTINELY PLACED IN AN ENCLOSED AREA, THE AREA SHOULD BE PROVIDED WITH ADEQUATE VENTILATION AND/OR A NATURAL GAS DETECTION SYSTEM. FOR LONG TERM STORAGE, THE MANUAL SHUTOFF VALVE AND EACH INDIVIDUAL FUEL CONTROL VALVE SHOULD BE CLOSED.
- A FIRE OR EXPLOSION COULD RESULT IF A SOURCE OF IGNITION OR FLAME IS PRESENT WITH NATURAL GAS IN A CONFINED-UNVENTILATED AREA. PROVIDE PROPER VENTILATION WHEN SERVICING CNG VEHICLES.
- NATURAL GAS CONTAINS AN ODOR ADDITIVE. OCCASIONALLY, MILD NATURAL GAS ODORS MAY BE NOTICED DURING ENGINE STARTING AND AFTER ENGINE SHUT DOWN. THIS IS BECAUSE OF SMALL QUANTITIES OF UNBURNED GAS IN THE ENGINE INTAKE AND EXHAUST MANIFOLDS. WHILE THESE ARE NORMAL, AS ARE GASOLINE ODORS IN SIMILAR CIRCUMSTANCES, A PERSISTENT ODOR OF NATURAL GAS INDICATES A LEAK IS PRESENT. HAVE THE VEHICLE CHECKED IMMEDIATELY FOR SOURCE OF LEAK. IF A LEAK IS DETERMINED TO EXIST, DO NOT BRING THE VEHICLE INTO AN UNVENTILATED AREA.
- DO NOT ATTEMPT TO WELD ANY PART OF THE FUEL CYLINDERS OR ANY OTHER FUEL SYSTEM COMPONENT.
- DO NOT ATTEMPT TO REFILL THE FUEL CYLINDERS IF ANY OF THE OUTER COMPOSITE (CYLINDER COVERING) HAS UNRAVELED.
- DO NOT ATTEMPT TO MODIFY ANY FUEL SYSTEM COMPONENT OR REPLACE ANY COMPONENT WITH PARTS THAT DO NOT MEET CHRYSLER CORPORATION REQUIREMENTS.
- DO NOT APPLY ANY PAINT OR UNDERCOATING MATERIAL TO ANY FUEL SYSTEM COMPONENT.
- DO NOT ATTEMPT TO FORCE OPEN OR TAMPER WITH ANY FUEL TUBES OR VALVES. A SUDDEN RELEASE OF HIGH-PRESSURE GAS MAY OCCUR RESULTING IN BODILY INJURY.
- DO NOT PARK OR SERVICE VEHICLE NEAR ANY SOURCE OF EXCESSIVE HEAT OR OPEN FLAMES.
- DO NOT USE A PAINT OVEN TO CURE ANY PAINT REPAIRS AS CNG FUEL CYLINDERS ON THESE VEHICLES ARE EQUIPPED WITH PRESSURE RELIEF SAFETY DEVICES. THESE DEVICES WILL VENT TO THE ATMOSPHERE AT APPROXIMATELY 103 DEGREES C (217 DEGREES F).
- WHEN A VEHICLE HAS BEEN INVOLVED IN AN ACCIDENT WHICH MAY HAVE CAUSED DAMAGE OR DISLOCATION TO THE CNG SYSTEM, THE SYSTEM SHOULD BE INSPECTED AND PRESSURE TESTED. THIS SHOULD BE DONE BEFORE BEING RETURNED TO SERVICE.
- ANY FUEL SYSTEM COMPONENT, INCLUDING THE CYLINDERS, THAT HAVE BEEN SUBJECTED TO FIRE, MAY NOT BE RETURNED TO SERVICE DUE TO REDUCED PRESSURE CAPABILITY
- U.S. REQUIREMENTS: EACH CNG FUEL CYLINDER MANUFACTURED ON OR AFTER MARCH 27, 1995 MUST BE REMOVED AND REINSPECTED AFTER A MOTOR VEHICLE ACCIDENT OR FIRE AND AT LEAST EVERY 36 MONTHS OR 36,000 MILES (WHICHEVER COMES FIRST) FOR DAMAGE AND DETERIORATION IN ACCORDANCE WITH MOTOR VEHICLE SAFETY STANDARD NO. 304 COMPRESSED NATURAL GAS FUEL CONTAINERS AND COMPRESSED GAS ASSOCIATION (CGA), ARLINGTON, VA. GUIDELINES C-6.4. RETEST MARKINGS MUST BE STAMPED ON THE CYLINDER NECK OR MARKED ON A LABEL SECURELY AFFIXED TO THE CYLINDER AND OVERCOATED WITH EPOXY NEAR THE ORIGINAL TEST DATE. REHEAT TREATMENT OR REPAIR OF REJECTED CYLINDERS IS NOT AUTHORIZED. THE FUEL CYLINDER EXPIRES AND MUST BE REMOVED FROM SERVICE FIFTEEN YEARS FROM THE DATE OF MANUFACTURE. A LABEL ON THE FUEL FILLER DOOR STATES THE CYLINDER RETEST DATE AND CYLINDER EXPIRATION DATE. A SIMILAR LABEL IS ATTACHED TO EACH FUEL CYLINDER. IF THERE IS A QUESTION ABOUT THE PROPER INSPECTION OF THE CNG CYLINDER, CONTACT THE MANUFACTURER AS IDENTIFIED ON THE CYLINDER LABEL.
- CANADIAN REQUIREMENTS: THE CYLINDER MUST BE REINSPECTED AFTER A MOTOR VEHICLE ACCIDENT OR FIRE AND AT LEAST EVERY 36 MONTHS OR 36,000 MILES (WHICHEVER COMES FIRST) FOR DAMAGE AND DETERIORATION IN ACCORDANCE WITH CANADIAN STANDARDS ASSOCIATION (CSA) B51-97, PART 2 HIGH-PRESSURE CYLINDERS FOR THE ONBOARD STORAGE OF NATURAL GAS AS A FUEL FOR AUTOMOTIVE VEHICLES AND COMPRESSED GAS ASSOCIATION (CGA), ARLINGTON, VA. GUIDELINES C-6.4. RETEST DATES MUST BE STAMPED ON THE EXPOSED METALLIC SURFACE OF THE CYLINDER NECK OR MARKED ON A LABEL SECURELY AFFIXED TO THE CYLINDER AND OVERCOATED WITH EPOXY NEAR THE ORIGINAL TEST DATE. REHEAT TREATMENT OR REPAIR OF REJECTED CYLINDERS IS NOT AUTHORIZED. THE FUEL CYLINDER EXPIRES AND MUST BE REMOVED FROM SERVICE FIFTEEN YEARS FROM THE DATE OF MANUFACTURE. A LABEL ON THE FUEL FILLER DOOR STATES THE FIRST CYLINDER RETEST DATE AND CYLINDER EXPIRATION DATE. IT IS RECOMMENDED THAT THE FUEL SYSTEM COMPONENTS BE INSPECTED PERIODICALLY FOR LEAKS AND/OR EXCESSIVE WEAR.
- FUEL THE VEHICLE USING A NGV I CERTIFIED FILL NOZZLE AS SPECIFIED ON THE LABEL INSIDE THE FUEL FILLER DOOR. DO NOT ATTEMPT TO FUEL THE VEHICLE WITH ANY OTHER TYPE OF NOZZLE.
- BEFORE ANY PART OF THE CNG FUEL SYSTEM IS OPENED FOR REPAIR, THE SYSTEM MUST BE PURGED OF ALL NATURAL GAS. REFER TO FUEL SYSTEM PURGING IN THIS SECTION.

FUEL CYLINDER - CNG ONLY

Fig.4 Rear Mounted Fuel Cylinders:

Fig.5 Side Mounted Fuel Cylinders:

Four high-pressure fuel cylinders are used to store Compressed Natural Gas (CNG). Two of the 4 cylinders are mounted transversely behind the rear axle (Fig. 4). The other 2 cylinders are mounted longitudinally along the left side of the vehicle frame rail (Fig. 5).

Both the Maxi and Standard size vans will share the same fuel cylinder configuration.

The 4 cylinders store natural gas at pressures up to approximately 3600 psi.

Each fuel cylinder is equipped with its own manually operated fuel control valve. Each of these valves is equipped with a pressure relief safety device. For more information, refer to Fuel Cylinder Control Valves.

Fig.6 Fuel Cylinder Expiration Data Label:

A label affixed to the fuel filler door (Fig. 6), states the first fuel cylinder (container) expiration date. A similar label is attached to each individual fuel cylinder. The label on the fuel cylinder will state: the address of the fuel cylinder manufacturer; the cylinder expiration date; certain warnings; and cylinder certification numbers.

Fig.19 Typical Fuel Control Valve And Pressure Relief Safety Device:

FUEL CYLINDER CONTROL VALVE/ CNG ONLY
Each of the 4 fuel cylinders is equipped with its own manually operated fuel control valve (Fig. 19).

The control valves are equipped with a pressure relief safety device (Fig. 19). This safety device is designed to release excess cylinder pressure to the atmosphere if the temperature rises above approximately 103 degrees C (217 degrees F). Turn the plastic valve handle fully clockwise to stop gas flow (closed). Turn the handle fully counterclockwise to provide gas flow (open).

FUEL FILL CHECK VALVE - CNG ONLY

Fig.21 One-Way Check Valve Location:

Two different one-way check valves are used with the CNG fuel system. One of the valves is located integrally within the fuel fill receptacle (Fig. 6). The other valve is located between the side mounted fuel cylinders near the manual (master) shut-off valve (Fig. 21).

Both valves are used to keep fuel from escaping from the fuel fill receptacle (fuel supply will only travel toward fuel cylinders). Refer to Fuel Fill Receptacle for additional information.

FUEL FILL RECEPTACLE - CNG ONLY
A filtered fuel fill receptacle is mounted in the con ventional area behind the fuel filler door (Fig 6)

The receptacle contains an integral one-way check valve. An additional one-way check valve is mounted near the manual (master) shut-off valve. Fuel the vehicle using a NGV 1 fill nozzle as specified on the label inside of the fuel filler door. Do not attempt to fuel the vehicle with any other type of nozzle.

Fig.27 Fuel Filter Location:

FUEL FILTER - CNG ONLY
The system fuel filter is mounted inside the fuel pressure regulator (Fig. 27). The fuel pressure regulator is mounted to a bracket located above the fuel cylinders on the left side of vehicle.

The fuel filter is used to stop small dirt particles from entering the fuel pressure regulator. The fuel filter is designed for extended service and does not require normal scheduled maintenance. The filter should only be replaced if a diagnostic procedure indicates to do so.

Fig.29 Fuel Gauge Pressure Sensor Location:

FUEL LEVEL SENDING UNIT / SENSOR - CNG ONLY
The fuel gauge pressure sensor (transducer) is mounted to a fuel control valve. This valve is located at the rear end of the left outer (side mounted) fuel cylinder (Fig. 29).

A three-wire (three-circuit), temperature compensated sensor (transducer) monitors fuel pressure in the high-pressure side of the fuel system. One of the wires supplies a 12 volt power source to the sensor. Another wire supplies a ground for the sensor. The third wire supplies a voltage signal from the sensor back to the Powertrain Control Module (PCM).

The sensor is used to vary its input voltage depending on fuel cylinder pressure. As fuel cylinder pressure increases, voltage decreases. As pressure decreases voltage increases. The voltage signal is returned back to the PCM through the sensor return circuit. The PCM will then interpret this resistance (voltage) data and send a message across the multiplex bus circuits to the instrument panel cluster. Here it is translated into the appropriate fuel gauge level reading. Refer to Instrument Panel for additional information. Output voltages from the sensor will vary from about 0.6 volts at FULL, to about 7.0 volts at EMPTY NOTE: For diagnostic purposes, this voltage can only be verified with the fuel gauge pressure sensor circuit closed (i.e. having all of the sensor circuits electrical connectors connected).

Fuel gauge calibration is the same as for gasoline powered models. For more information, refer to Instrument Panel and Gauges.

The electrical circuits between the fuel gauge pressure sensor and the PCM are hard-wired (not multiplexed).

FUEL LINES - CNG ONLY
Due to the high-pressure requirements of the CNG system, special stainless steel, SAE straight thread O-ring, single-ferrule, silver plated compression-type fuel tube fittings are used. These will connect all fuel tubes and components on the high-pressure side of the system (inlet side of the fuel pressure regulator).

High-pressure stainless steel, seamless fuel tubes are also used.

Standard NPT and 45 degree fittings using O-rings are used on the low-pressure side of the system (downstream or outlet side of the fuel pressure regulator).

Due to special service requirements, also refer to the special WARNINGS AND SAFETY PRECAUTIONS section before attempting any repair.

WARNING
- DUE TO THE EXTREME HIGH PRESSURES OF THE CNG FUEL SYSTEM, CERTAIN PRECAUTIONS MUST BE TAKEN WHEN HANDLING OR SERVICING FUEL TUBES OR FUEL TUBE FITTINGS:
- WHERE APPLICABLE, USE ONLY SINGLE- FERRULE COMPRESSION TYPE FITTINGS ON THE CNG SYSTEM. IF A FITTING MUST BE REPLACED, USE ONLY AN ORIGINAL EQUIPMENT REPLACEMENT PART.
- WHEN HANDLING FUEL TUBES, DO NOT ALLOW ENDS OF TUBES TO GET SCRATCHED. SMALL SCRATCHES ARE A POTENTIAL SOURCE OF A LEAK.
- ALWAYS CHECK AND REMOVE ANY BURRS FROM THE END OF TUBES BEFORE INSTALLING FITTINGS.
- AFTER SOME TYPES OF HIGH-PRESSURE FITTINGS ARE TIGHTENED, A GO NO-GO GAUGE INSPECTION TOOL MUST BE USED. THIS IS TO BE SURE THEY ARE PROPERLY DRAWN UP (TIGHTENED).
- DO NOT ATTEMPT TO REMOVE OR TIGHTEN A FITTING WITH THE FUEL SYSTEM UNDER PRESSURE.
- SURFACE FINISH OF THE FUEL TUBE IS VERY IMPORTANT FOR PROPER SEALING. FUEL TUBES THAT ARE OVAL SHAPED, HAVE ANY DEPRESSIONS, HEAVY SCRATCHES OR RAISED PORTIONS SHOULD NOT BE USED.
- NEVER ATTEMPT TO FORCE A FUEL TUBE INTO A FITTING OR FERRULE. THE FUEL TUBE SHOULD FIT EASILY INTO FITTINGS/FERRULES IF THEY ARE NOT DAMAGED.
- THE FUEL TUBES ON THE CNG SYSTEM ARE UNDER EXTREME HIGH-PRESSURE. NEVER USE STEEL, COPPER, BRASS OR ANY OTHER MATERIAL AS A SUBSTITUTE FOR THE ORIGINAL SEAMLESS STAINLESS STEEL FUEL TUBES.
- WHEN REMOVING/INSTALLING A FITTING, ALWAYS USE A BACKUP WRENCH ON THE FITTING BODY TO PREVENT ANY FUEL TUBE TWIST.

FUEL PRESSURE REGULATOR - CNG ONLY

Fig.36 Fuel Pressure Regulator Location:

Fig.37 Fuel Pressure Regulator Mounting:

The fuel pressure regulator is located above the fuel cylinders on left side of vehicle (Fig. 36). It is mounted to the fuel cylinder carrier (support) bracket (Fig. 37).

The regulator is used to lower fuel cylinder pressure from approximately 3600 psi down to approximately 110-125 psi for system operation. This is with the engine fully warmed.

The regulator contains a built-in pressure relief safety device. The device is used only as a safety and does not effect fuel system operation. This device is located on the low-pressure side of the regulator (Fig. 38) and will relieve excess pressure to the atmosphere above approximately 225 psi (determined at low-pressure side of regulator). A pressure relief discharge tube (Fig. 36) is routed to the left side of the vehicle.

Fig.38 Fuel Pressure Regulator Components:

The pressure regulator also contains the system fuel filter (Fig. 38).

Engine coolant is used to help warm the fuel pressure regulator. This is done to counteract the thermodynamic cooling effect as natural gas is expanded (gas pressure dropped).

Two rubber heater hoses are used to connect the fuel pressure regulator to the engine cooling system. The hoses are teed into the vehicle heater hoses in the engine compartment. They are routed along the vehicle underbody directly to fuel pressure regulator. For service, refer to Cooling System.

FUEL PRESSURE REGULATOR HOSE - CNG ONLY
Two rubber hoses are used to connect the fuel pressure regulator (Fig. 38) to the engine cooling system. The hoses are teed into the vehicle heater hoses in the engine compartment.

Engine coolant is used to help warm the fuel pressure regulator. This is done to counteract the thermodynamic cooling effect as natural gas is expanded (gas pressure dropped).

Refer to Fuel Pressure Regulator for additional information For hose service, refer to Cooling System

Fig.18 Fuel Gauge Pressure Sensor (Transducer):

FUEL PRESSURE SENSOR - CNG ONLY
The fuel low-pressure sensor is located on the right side of the fuel injector rail (Fig. 18)

This fuel low-pressure sensor signal, along with other sensors, will provide for calculation of fuel injector timing through the Powertrain Control Module (PCM).

FUEL RAIL - CNG ONLY
A unique fuel injector rail (Fig. 18) is used with the CNG fuel system.

The fuel rail supplies the necessary fuel to each individual fuel injector and is mounted to the intake manifold.

NOTE: The left and right sections of the fuel rail are connected with a (non-serviceable) flexible connecting hose (Fig. 18). Do not attempt to separate the rail halves at this connecting hose. Due to the design of this connecting hose, it does not require any clamps. Never attempt to install a clamping device of any kind to the hose. When removing the fuel rail assembly for any reason, be careful not to bend or kink the connecting hose.

HI PRESSURE FUEL SHUTOFF SOL - CNG ONLY
The high-pressure fuel shut-off solenoid is an integral part of the fuel pressure regulator (Fig. 37) or (Fig. 38).

The high-pressure fuel shut-off solenoid is used as an on/off valve to electrically control high-pressure gas flowing through the fuel pressure regulator. It is operated by the Powertrain Control Module (PCM). This is accomplished through the high-pressure fuel shut-off solenoid relay. Also refer to High-Pressure Fuel Shut-Off Solenoid Relay.

Fig.46 High-Pressure Fuel Shut-Off Solenoid Relay Location:

HI PRESSURE FUEL SHUTOFF SOLENOID RELAY - CNG ONLY
The high-pressure fuel shut-off solenoid relay is located in the Fuse and Relay Block at the left end of the instrument panel (Fig. 46).

This high-pressure fuel shut-off solenoid relay is used in place of the conventional fuel pump relay. It is used to electrically control operation of the highpressure fuel shut-off solenoid. The solenoid is located within the fuel pressure regulator.

The Powertrain Control Module (PCM) operates the high-pressure fuel shut-off solenoid relay through a ground path.

The PCM turns the ground path off when the ignition switch is in the OFF position. When the ignition switch is in the ON or CRANK position, the PCM monitors the crankshaft position sensor and camshaft position sensor signals to determine engine speed and ignition timing (coil dwell). If the PCM does not receive the necessary crankshaft position sensor and camshaft position sensor signals when the ignition switch is in the Run position (indicating the engine has not started and is not running), it will deenergize the relay.

Fig.48 Low-Pressure Fuel Shut-Off Solenoid Location:

LOW PRESSURE FUEL SHUTOFF SOLENOID - CNG ONLY
The low-pressure fuel shut-off solenoid is mounted to the left side of (inlet side of) the fuel injector rail (Fig. 48).

The low-pressure fuel shut-off solenoid is controlled by the Powertrain Control Module (PCM) through a 12 volt + output from the Automatic Shut-Down (ASD) relay. After high cylinder pressure has been lowered by the fuel pressure regulator, this solenoid is used as an on/off valve to electrically control natural gas entering the fuel rail assembly. When the ignition switch is in the OFF position, fuel supply is shut off to the engine. Refer to ASD relay for additional information.

MANUAL SHUTOFF VALVE - CNG ONLY

Fig.52 Manual Valve Location Label:

A one-quarter turn, manual (master) shut-off valve is located under the vehicle between the 2 left-side mounted fuel cylinders. Its location is identified by a label; MANUAL SHUT-OFF VALVE affixed to the left-outer side of the vehicle body (Fig. 52). The valve handle is red in color.

Fig.53 Longitudinal Handle Position - Gas Flow Open:

Fig.54 Cross Handle Position - Gas Flow Stopped:

When the manual shut-off valve handle is in the longitudinal position (parallel with fuel cylinders) (Fig. 53), gas is allowed to flow to the fuel pressure regulator and on to the engine. When the handle is in the cross position (not parallel with fuel cylinders) (Fig. 54), fuel flow is stopped. Each fuel cylinder is also equipped with its own manually operated and independently controlled fuel control valve.