Compressed Natural Gas (CNG) Temperature vs Percent Full
| KPa (psi) 1 | 50° C (-18° F) 2 | 30° C (3° F) 2 | 9° C (23° F) 2 | 11° C (43° F) 2 | 32° C (54° F) 2 | 53° C (84° F) 2 | 73° C (105° F) 2 | 93° C (125° F) 2 | 114° C (146° F) 2 | 134° C (166° F) 2 | 156° C (187° F) 2 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 2825 (410) | 17% | 15% | 13% | 12% | 11% | 11% | 10% | 9% | 9% | 8% | 8% |
| 5650 (819) | 40% | 34% | 29% | 26% | 24% | 22% | 20% | 19% | 18% | 17% | 16% |
| 8474 (1229) | 79% | 59% | 49% | 41% | 38% | 34% | 31% | 29% | 27% | 25% | 24% |
| 11299 (1638) | 115% | 87% | 70% | 56% | 50% | 45% | 41% | 38% | 36% | 33% | 31% |
| 14124 (2048) | 122% | 109% | 85% | 73% | 65% | 60% | 53% | 48% | 45% | 42% | 39% |
| 16949 (2458) | 122% | 122% | 101% | 88% | 79% | 71% | 65% | 58% | 54% | 50% | 47% |
| 19774 (2867) | 122% | 122% | 116% | 100% | 90% | 81% | 75% | 67% | 63% | 59% | 55% |
| 22599 (3277) | 122% | 122% | 122% | 112% | 100% | 92% | 83% | 76% | 70% | 66% | 62% |
| 25453 (3686) | 122% | 122% | 122% | 122% | 109% | 100% | 90% | 84% | 78% | 74% | 70% |
| 28248 (4096) | 122% | 122% | 122% | 122% | 111% | 103% | 96% | 90% | 84% | 80% | 76% |
| 1 This indicates the fuel pressure inside the CNG fuel tank. 2 This indicates the temperature of the fuel inside the CNG fuel tank. Use the table in order to determine the amount of fuel vs fuel tank capacity. | |||||||||||
Compressed Natural Gas (CNG) Temperature vs Percent Full
Fuel Tank Pressure (FTP) Sensor Output Voltage vs Pressure
| KPa (psi) | Voltage |
|---|---|
| 0 (0) | 0.50 |
| 862 (125) | 0.63 |
| 3 021 (438) | 0.94 |
| 5 172 (750) | 1.25 |
| 7 331 (1,063) | 1.56 |
| 9 483 (1,375) | 1.88 |
| 11 641 (1,688) | 2.19 |
| 13 793 (2,000) | 2.50 |
| 15 952 (2,313) | 2.81 |
| 18 103 (2,625) | 3.13 |
| 20 262 (2,938) | 3.44 |
| 22 414 (3,250) | 3.75 |
| 24 572 (3,563) | 4.06 |
| 26 724 (3,875) | 4.38 |
| 27 586 (4,000) | 4.54 |
Fuel Tank Pressure (FTP) Sensor Output Voltage vs Pressure
Fuel Rail Pressure (FRP) Sensor Output Voltage vs Pressure
| KPa (psi) | Voltage |
|---|---|
| 0 (0) | 0.5 |
| 68.95 (10) | 0.9 |
| 137.9 (20) | 1.3 |
| 206.85 (30) | 1.7 |
| 275.8 (40) | 2.1 |
| 344.75 (50) | 2.5 |
| 413.7 (60) | 2.9 |
| 482.65 (70) | 3.3 |
| 551.6 (80) | 3.7 |
| 620.55 (90) | 4.1 |
| 689.5 (100) | 4.5 |
Fuel Rail Pressure (FRP) Sensor Output Voltage vs Pressure
Fuel Tank Temperature (FTT) Sensor Output Voltage vs Temperature Resistance
| ° C (° F) | Voltage | Resistance |
|---|---|---|
| 50 (-58) | 4.87 | 104,390 |
| 40 (-40) | 4.77 | 57,536 |
| 20 (-4) | 4.38 | 19,326 |
| 5 (23) | 3.86 | 9,311 |
| 0 (32) | 3.65 | 7,407 |
| 5 (41) | 3.42 | 5,933 |
| 10 (50) | 3.18 | 4,764 |
| 15 (59) | 2.93 | 3,881 |
| 20 (68) | 2.68 | 3,167 |
| 25 (77) | 2.43 | 2,600 |
| 30 (86) | 2.20 | 2,148 |
| 35 (95) | 1.97 | 1,784 |
| 40 (104) | 1.76 | 1,489 |
| 45 (113) | 1.57 | 1,249 |
| 50 (122) | 1.39 | 1,052 |
| 60 (140) | 1.08 | 758 |
| 70 (158) | 0.84 | 556 |
| 80 (176) | 0.66 | 414 |
| 100 (212) | 0.40 | 240 |
| 120 (248) | 0.26 | 147 |
| 150 (302) | 0.14 | 77 |
Fuel Tank Temperature (FTT) Sensor Output Voltage vs Temperature Resistance
Fuel Temperature Sensor (FTS) Output Voltage vs Temperature Resistance
| ° C (° F) | Voltage | Resistance |
|---|---|---|
| 50 (-58) | 4.87 | 104,390 |
| 40 (-40) | 4.77 | 57,536 |
| 20 (-4) | 4.38 | 19,326 |
| 5 (23) | 3.86 | 9,311 |
| 0 (32) | 3.65 | 7,407 |
| 5 (41) | 3.42 | 5,933 |
| 10 (50) | 3.18 | 4,764 |
| 15 (59) | 2.93 | 3,881 |
| 20 (68) | 2.68 | 3,167 |
| 25 (77) | 2.43 | 2,600 |
| 30 (86) | 2.20 | 2,148 |
| 35 (95) | 1.97 | 1,784 |
| 40 (104) | 1.76 | 1,489 |
| 45 (113) | 1.57 | 1,249 |
| 50 (122) | 1.39 | 1,052 |
| 60 (140) | 1.08 | 758 |
| 70 (158) | 0.84 | 556 |
| 80 (176) | 0.66 | 414 |
| 100 (212) | 0.40 | 240 |
| 120 (248) | 0.26 | 147 |
| 150 (302) | 0.14 | 77 |
Fuel Temperature Sensor (FTS) Output Voltage vs Temperature Resistance
Fuel Rail Temperature (FRT) Sensor Output Voltage vs Temperature Resistance
| ° C (° F) | Voltage | Resistance |
|---|---|---|
| 50 (-58) | 4.97 | 1,579,500 |
| 40 (-40) | 4.93 | 1,070,550 |
| 20 (-4) | 4.74 | 186,000 |
| 0 (32) | 4.24 | 55,620 |
| 10 (50) | 3.81 | 32,100 |
| 20 (68) | 3.29 | 19,185 |
| 25 (77) | 3.00 | 15,000 |
| 30 (86) | 2.71 | 11,818.50 |
| 35 (95) | 2.42 | 9,376.50 |
| 40 (104) | 2.14 | 7,489.50 |
| 45 (113) | 1.88 | 6,021.00 |
| 50 (122) | 1.64 | 4,870.50 |
| 60 (140) | 1.23 | 3,250.50 |
| 70 (158) | 0.91 | 2,218.50 |
| 80 (176) | 0.67 | 1,543.50 |
| 100 (212) | 0.37 | 789.75 |
| 120 (248) | 0.21 | 433.80 |
| 145 (293) | 0.11 | 220.95 |
Fuel Rail Temperature (FRT) Sensor Output Voltage vs Temperature Resistance
Engine Controls Components
| Name | Location | Locator View | Connector End View |
|---|---|---|---|
| AF Fuel Mode Relay | AF Relay Block Left-Underhood | Engine Controls Component Views | Engine Controls Connector End Views |
| AF Lock-off Relay | Left side of engine compartment attached to fuse block-underhood | Engine Controls Component Views | Engine Controls Connector End Views |
| AFS/Ign 0 Fuse | In fuse block-left I/P | Engine Controls Component Views | |
| AFS/PCM1 Fuse | In fuse block-underhood | Engine Controls Component Views | |
| AFS/4WS Fuse | In fuse block-underhood | Engine Controls Component Views | |
| Fuel Gage Selector Switch | Right side of I/P below radio | Engine Controls Component Views | Engine Controls Connector End Views |
| Fuel Injector Control Module (FICM) | Right side of engine compartment below the air filter assembly | Engine Controls Component Views | Fuel Injection Control Module Connector End Views |
| Fuel Rail Pressure (FRP) Sensor | Center of CNG fuel rail-Left | Engine Controls Component Views | Engine Controls Connector End Views |
| Fuel Rail Temperature (FRT) Sensor | Center of CNG fuel rail-Right | Engine Controls Component Views | Engine Controls Connector End Views |
| Fuel Tank Pressure (FTP) Sensor | Threaded into HPL | Engine Controls Component Views | Engine Controls Connector End Views |
| Fuel Tank Temperature (FTT) Sensor | Non-serviceable part of HPL | Engine Controls Component Views | Engine Controls Connector End Views |
| High Pressure Lock-off (HPL) | Threaded into CNG tank end | Engine Controls Component Views | Engine Controls Connector End Views |
| High Pressure Regulator (HPR) | Attached to CNG fuel tank lower support bracket | Engine Controls Component Views | |
| Injector Power Relay-Even Bank | AF Relay Block Right-underhood (KL6) Attached to left fender to cowl support brace (KL8) | Engine Controls Component Views | Engine Controls Connector End Views |
| Injector Power Relay-Odd Bank | AF Relay Block Left-underhood (KL6) Attached to left fender to cowl support brace (KL8) | Engine Controls Component Views | Engine Controls Connector End Views |
| Injector Relays #1,3,5,7 | AF Relay Block Left-underhood | Engine Controls Component Views | Engine Controls Connector End Views |
| Injector Relays #2, 4, 6, 8 | AF Relay Block Right-underhood | Engine Controls Component Views | Engine Controls Connector End Views |
| Inline AF Fuses | Left side of engine compartment attached to rear of fuse block-underhood cover | ||
| Intermediate Pressure Regulator (IPR) | Left side of engine above valve rocker cover | Engine Controls Component Views | |
| Low Pressure Lock-off (LPL) | Left side of engine above valve rocker cover | Engine Controls Component Views | Engine Controls Connector End Views |
| C001 | Right side of engine compartment below the air filter assembly at FICM | Engine Controls Component Views | Fuel Injection Control Module Connector End Views |
| C002 | Left side of engine compartment near fuse block-underhood FICM harness breakout | Engine Controls Component Views | Engine Controls Connector End Views |
| C003 | Left side of engine compartment near fuse block-underhood FICM harness breakout | Engine Controls Component Views | Engine Controls Connector End Views |
| C004 | Left side of engine compartment near fuse block-underhood FICM harness breakout | Engine Controls Component Views | Engine Controls Connector End Views |
| C005 | Left side of engine compartment near fuse block-underhood engine harness breakout (KL6) | Engine Controls Component Views | Engine Controls Connector End Views |
| C006 | Left side of engine compartment attached to IPR/LPL mounting bracket | Engine Controls Component Views | Engine Controls Connector End Views |
| C007 | Right rear side of engine near transmission dipstick tube | Engine Controls Connector End Views | |
| C008 | Left side of engine compartment near fuse block-underhood FICM harness breakout | Engine Controls Component Views | Engine Controls Connector End Views |
| C009 | Behind truck cab attached to left front pickup box support frame | Engine Controls Connector End Views | |
| C010 | Left side of engine compartment near throttle actuator motor (TAC) module harness breakout | Engine Controls Connector End Views |
Engine Controls Components
Scheme 486
| Callout | Component Name |
|---|---|
| 1 | Inline Connector C004 |
| 2 | Inline Connector C005, C006 |
| 3 | Lock-off Solenoid Relay Connector |
| 4 | Injector Relays - Even Bank |
| 5 | Injector Relays - Odd Bank |
| 6 | AF Fuel Mode Relay |
| 7 | In-Line AF Fuses |
| 8 | Fuel Tank Pressure Sensor Connector |
| 9 | Fuel Tank Pressure (FTP) Sensor |
| 10 | CNG Fuel Tank |
| 11 | High Pressure Lock-off (HPL) Solenoid Connector |
| 12 | High Pressure Lock-off (HPL) Solenoid |
| 13 | Fuel Tank Temperature (FTT) Sensor Connector |
| 14 | Low Pressure Lock-off (LPL) Solenoid Connector |
| 15 | Low Pressure Lock-off (LPL) Solenoid |
| 16 | Intermediate Pressure Regulator (IPR) |
| 17 | Fuel Rail Pressure (FRP) Sensor Connector |
| 18 | Left Hand Gaseous Fuel Rail |
| 19 | Gaseous Fuel Injector |
| 20 | Gaseous Fuel Injector Connector |
| 21 | Fuel Rail Temperature (FRT) Sensor Connector |
| 22 | Right Side Inner Fender |
| 23 | Alternative Fuel Injector Control Module (FICM) Connector C001 |
| 24 | Alternative Fuel Injector Control Module (FICM) |
Scheme 487
| Callout | Component Name |
|---|---|
| 1 | Left Hand Gaseous Fuel Rail |
| 2 | Right Hand Gaseous Fuel Rail |
| 3 | Gaseous Fuel Injector (1 of 8) |
| 4 | High Pressure Regulator (HPR) Coolant Lines |
| 5 | High Pressure Regulator (HPR) |
| 6 | Inline CNG Fuel Filter |
| 7 | High Pressure Lock-off (HPL) Fitting CNG Fuel Line |
| 8 | Pick-up Box Floor |
| 9 | CNG Fuel Fill Valve |
| 10 | CNG Fuel Fill Line |
| 11 | Left Hand Vehicle Frame Rail |
| 12 | Chassis CNG Fuel Line |
| 13 | Chassis Fuel Line Pick-up Box Pass-through |
| 14 | Low Pressure Lock-off (LPL) Solenoid CNG Fuel Line Inlet Fitting |
| 15 | Low Pressure Lock-off (LPL) Solenoid |
| 16 | Intermediate Pressure Regulator (IPR) |
Scheme 488
Scheme 489
Scheme 490
Fuel Pressure Relief Procedure
- With a scan tool communicate with the powertrain control module (PCM). If communication cannot be established and the «Diagnostic System Check - Alternative Fuels (Engine Controls)»(ref-184499-S02000137622005082300000) has already been performed proceed to Step 9.
- Store the DTC Information with a scan tool.
- Clear the DTC Information with a scan tool.
- Turn OFF the ignition.
- Start and idle the engine.
- Ensure that the engine is operating on CNG by observing the following: The fuel indicator lamp (FIL) is OFF (KL6). The AFO Enable scan tool display indicates the engine is operating on alternative fuel.
- With a scan tool, select the high pressure lock-off (HPL) solenoid special function.
- While the engine is operating on CNG command the HPL solenoid OFF and observe the fuel tank pressure sensor data parameter. The fuel tank pressure should slowly decrease. If the fuel pressure fails to decrease proceed to Step 9. When the engine stalls or a switch-over to gasoline is observed, perform the following: Turn OFF the ignition. IMPORTANT: Turning the ignition ON with the AF lock-off relay disconnected may set a DTC. Clear DTC Information after repairs are complete. Disconnect the alternate fuels lock-off relay connector in order to disable the CNG fuel system. A small amount of CNG will remain in the fuel lines and components. Slowly open the fittings in order to release any remaining pressure when disconnecting a fuel line. Fuel pressure relief for the CNG system is now complete. Proceed to Step 16.
- Close the manual lock-down screw located on the end of the HPL solenoid. The manual shut-off fitting is closed by rotating the Allen screw clockwise until fully seated.
- Turn OFF the ignition.
- Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnect/Connect Procedure (Single Battery) Battery Negative Cable Disconnect/Connect Procedure (Auxiliary Battery) in Engine Electrical in the C/K Truck service manual.
- Slowly loosen the fuel line fitting (1) at the low pressure lock-off solenoid elbow (2) several turns.
- Fuel Pressure Relief for the CNG system is complete when the fuel line can be pulled away from the O-ring face seal and fuel does not vent.
- Replace the O-ring face seals at all fittings that were disconnected or loosened.
- After all necessary repairs are complete perform the following: Tighten any loosened fittings to the correct torque. Refer to «Fastener Tightening Specifications»(ref-184498-S07034226902005082300000) IMPORTANT: Leave the manual lock-down screw closed on any vehicle that will require CNG fuel tank venting. Open the manual lock-down screw located on the HPL manual shut-off fitting by rotating the Allen screw counterclockwise until fully seated on any vehicle that does not require venting of the CNG fuel tanks.
- If the service necessary for the vehicle requires the CNG fuel tanks to be relieved of all internal pressure, refer to «Fuel Tank Venting Procedure»(ref-184498-S14125958572005082300000)
Dents
| IMPORTANT | Replace tanks with dents to the metal edges greater than 1.52 mm (0.060 in) deep. |
Gouges
| IMPORTANT | Replace tanks with sharp gouges penetrating the paint and the metal. |
Removing From Service
- The CNG fuel tank has a fifteen year service life from the date of manufacture.
- The CNG tank manufacture date appears on a label on the tank.
- The tank expiration date is also on the underhood and fill area labels.
- Any tank in service for 15 years or more must be removed from service using the following procedure: Remove and vent the tank. Refer to the latest service procedures. Disconnect the vent hose. Place the tank outside in a well ventilated area. Allow the tank to stand for 24 hours with the manual valve opening tool installed. Drill a 1/4 inch hole after the last digit of the tank identification number stamped into the valve end of the tank. Dispose of the tank in a safe and approved manner.
Tools Required
J 42435 CNG Tank Venting Kit. See Special Tools and Equipment .
Fuel Tank Venting
- Remove the CNG fuel tank cover. Refer to «Fuel Tank Cover Replacement»(ref-184498-S06677910822005082300000) . Remove the truck body or side panel as required on ZW9 equipped vehicles in order to gain access to the right side of the CNG fuel tank.
- Relieve the fuel system pressure. Refer to «Fuel Pressure Relief Procedure»(ref-184498-S35460101902005082300000) .
- Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnect/Connect Procedure (Single Battery) Battery Negative Cable Disconnect/Connect Procedure (Auxiliary Battery) in Engine Electrical in the C/K Pickup service manual.
- Disconnect the fuel outlet line (4) from the HPL tee fitting (3).
- Disconnect the tee fitting (3) from the HPL inlet fitting (2).
- Remove the HPL inlet fitting (2).
- Remove the fuel tank pressure (FTP) sensor (2).
- Install fittings (2, 4, 8) supplied from the J 42435 into all of the HPL fuel ports as necessary. See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) . It is not necessary to install a fitting and cap in the pressure relief device (PRD) outlet port (6). Tighten: Tighten the fittings to 48 N.m (35 lb ft).
- Install caps supplied from the J 42435 onto the FTP port fitting (2) and the fuel outlet fitting (8) as necessary. See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) . Tighten: Tighten the caps to 37 N.m (27 lb ft).
- Connect the female end of the vent hose to the fuel line fitting.
- Connect the male end of the vent hose (6) to a vent stack. Refer to the J 42435 container for instructions on how to properly construct a vent stack. See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) .
- Connect the ground strap (4) to the FTP port fitting (3) and to the vent stack earth ground (5).
- Ensure that the manual lock-down screw of the manual shut-off fitting (2) is open by rotating the Allen screw counterclockwise until fully seated.
- If the tank begins venting when the manual lock-down screw is opened do not proceed to the next step until the tank stops venting.
- Remove the manual shut-off fitting from the HPL.
- Obtain the manual vent tool supplied from the J 42435 . See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) .
- Rotate the screw on the manual vent tool counterclockwise in order to fully retract the plunger.
- Install the manual vent tool into the HPL port with the plunger fully retracted. Tighten: Tighten the manual vent tool to 12 N.m (108 lb in).
- Slowly turn the manual vent tool screw clockwise until the plunger is fully extended.
- Open the J 42435 in-line valve. See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) . The tank should always contain some pressure and begin to vent.
- Allow the CNG fuel tank to vent until the pressure gauge reads 0 kPa (0 psi). If the tank stops venting and pressure is indicated on the J 42435 gauge, inspect the vent line for a frozen fitting. See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) . The fitting will eventually thaw and fuel will again continue to vent. Inspect for freezing near the HPL. A frozen HPL may stop fuel flow temporarily and show 0 kPa (0 psi) on the pressure gauge.
- When the tank is completely vented remove the vent line (6) from the fuel fitting.
- Remove all the fittings and caps as necessary.
- Remove the manual vent tool (2).
- If the tank is to be re-used replace the high pressure lock-off. Refer to «High Pressure Lock-Off (HPL) Solenoid Replacement»(ref-184498-S07282428232005082300000) .
J 44244 CNG Tank Support Harness. See Special Tools and Equipment .
Fuel Tank Cleaning
- Perform the «Fuel Pressure Relief Procedure»(ref-184498-S35460101902005082300000) .
- Perform the «Fuel Tank Venting Procedure»(ref-184498-S14125958572005082300000) .
- Perform the high pressure lock-off (HPL) removal procedure leaving the HPL installed into the tank finger-tight. Refer to «High Pressure Lock-Off (HPL) Solenoid Replacement»(ref-184498-S07282428232005082300000) .
- Place the J 44244 (1) on the shop floor. See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) .
- Lower the CNG fuel tank (2) on top of the J 44244 (1). See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) .
- Place the J 44244 support flap so that the HPL (3) protrudes through the flap. See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) .
- Place the J 44244 (1) straps around the CNG fuel tank placing the end strap over the HPL (3) and around the neck of the CNG fuel tank. See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) .
- Securely fasten the J 44244 straps (2) around the CNG fuel tank (1). See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) . Longer CNG fuel tanks will require the use of all the J 44244 straps. See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) .
- Connect the J 44244 to a suitable lifting device. See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) .
- Slowly raise the CNG fuel tank (1) until the HPL (2) is above the ground ensuring that the HPL does not contact the floor during the lifting process.
- Place a container (3) underneath the HPL (2) in order to collect any drained fluids.
- Remove the HPL (2), allowing any fluids to drain completely from the CNG fuel tank.
- Dispose of any collected fluids in a safe and approved manner.
- Flush the inside of the CNG fuel tank using clean water.
- Dry the inside of the CNG fuel tank using compressed air.
- Install the HPL (2) finger-tight.
- Slowly lower the CNG fuel tank (1) back to the ground ensuring the HPL does not contact the ground.
- Remove the J 44244 (1) from the CNG fuel tank (2). See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) .
- Complete the installation of the HPL into the tank and the tank into the vehicle by completing the installation steps as indicated in the «High Pressure Lock-Off (HPL) Solenoid Replacement»(ref-184498-S07282428232005082300000) .
- J 45529 Tank Removal Tool. See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) .
- J 45878 Combustible Gas Detector. See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) .
- J 45529 Tank Removal Tool. See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) .
- J 45878 Combustible Gas Detector. See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
- J 43602 HPL Crowfoot - 2. See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) 0.5 inch
- J 45529 Tank Removal Tool. See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) .
- J 45878 Combustible Gas Detector. See «Special Tools and Equipment»(ref-184498-S25171947842005082300000) .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
J 45878 Combustible Gas Detector. See Special Tools and Equipment .
Powertrain Control Module (PCM)
The PCM controls fuel delivery and for KL6 vehicles, determines which fuel system the engine is operating on. The PCM monitors various engine and vehicle functions to provide the correct amount of CNG or gasoline fuel under all operating conditions. This provides excellent driveability and fuel economy while maintaining reduced emission levels. When operating on CNG, the PCM opens the AFO enable circuit. When the AFO enable circuit is open, the fuel injector control module (FICM) will sequentially operate the CNG fuel injectors. A FICM is required because the PCM is not capable of operating the high current CNG fuel injectors. The PCM injector pulse width signals are received by the FICM and duplicate pulse width signals are generated by the FICM in order to operate the CNG injectors.
The PCM monitors 2 PWM signals from the FICM in order to determine CNG fuel tank pressure, CNG fuel tank temperature, CNG fuel rail temperature, and the diagnostic status of the FICM. The FICM monitors the CNG fuel tank pressure sensor, CNG fuel tank temperature sensor, and the CNG fuel rail temperature sensor. This information is communicated to the PCM by a dedicated PWM circuit. The FICM also performs internal diagnostics, and communicates this information by a dedicated PWM circuit. For further detail refer to Fuel Injector Control Module Description .
The PCM controls the Low Pressure Lock-Off (LPL) solenoid, and the High Pressure Lock-Off (HPL) solenoid. The PCM commands the HPL solenoid open for 1 second at every ignition ON, in order to prime the CNG fuel system. The PCM commands the HPL, and the LPL open when the engine is cranking or running on CNG.
When operating on gasoline, the PCM will send a message to the instrument panel (IP). The IP will display a message indicating the vehicle is running on gasoline.
The PCM also determines the CNG fuel level. The PCM monitors the FTP and FTT sensor information that is sent from the FICM. The FTP and FTT sensors are located on the CNG tank high pressure lock-off solenoid. The PCM performs a calculation of the CNG pressure and CNG temperature in order to determine an accurate CNG fuel level. On Bi-fuel (KL6) models the gasoline fuel level is determined by the PCM in a conventional manner using an in-tank variable resistor sensor. A fuel gage select switch allows the vehicle operator the ability to request momentary fuel gage display of either fuel level regardless of the fuel system in operation.
For further PCM description refer to Powertrain Control Module (PCM) Description in Engine Controls in the C/K Pickup Service Manual.
Sensor PWM Circuit
The FRT sensor information is required by the PCM for fuel trim adjustment. The FTP and FTT sensors information is required by the PCM for fuel gage operation. The PCM does not have the ability to supply and monitor the FRT, FTP and FTT sensors. The FICM performs this task by supplying the sensors a 5-volt reference, low reference and signal circuit. The signal voltage of the sensors are converted into a PWM signal. The PWM signal is sent to the PCM through a dedicated circuit. The PCM converts the PWM signal into pressure and temperature values.
Fuel Supply Components
The alternative fuels supply system consists of the following components
- Fuel Tank
- Fuel Tank Pressure Relief Device (PRD)
- Fill Valve and Fill Line
- High Pressure Lock-Off (HPL) Solenoid
- Fuel Tank Pressure Sensor
- Fuel Tank Temperature Sensor
- Fuel Lines
- Coalescing CNG Fuel Filter
Fuel Tank
Two kinds of fuel tanks are available. A Type 2 CNG fuel tank is constructed of steel and is wrapped in carbon fiber set in epoxy. A Type 4 CNG fuel tank is constructed of composite material and is wrapped in fiberglass and epoxy. A high pressure lock-off solenoid is contained within the fuel tank and is used to prevent fuel flow during non-cranking or running engine conditions. Fuel tanks have a protective cover. The cover is designed to protect the tank from damage due to shifting cargo and also for ultra-violet (UV) radiation protection. The cover is not designed to support a load. Federal government regulations require that the fuel tank and brackets be inspected every 3 years or 60 000 km (36,000 mi), whichever comes first. Fuel tank inspection results should be recorded in the CNG Fuel Tank Inspection Record area of the owners manual supplement. The service life of the CNG fuel tank can be 15 years or 20 years from the date of manufacture. All CNG fuel tanks regardless of inspection results must be replaced after their expiration date has passed. The CNG fuel tank expiration date is always listed on the tank label. Refer to Fuel Tank Inspection (Type 2 Tank) procedures.
Fuel Tank Pressure Relief Device (PRD)
The CNG fuel tank is equipped with a thermally activated PRD valve. The PRD is necessary in order to protect the CNG fuel tank from excessive pressure build-up in the event the tank is exposed to high temperatures. The PRD is sealed internally with a thermally sensitive metal valve. When the PRD is exposed to temperatures near 102° C (215° F), the metal valve will melt and allow the CNG fuel tank pressure to fully vent to the atmosphere. The PRD will not close once activated. On Type 2 fuel tanks the PRD is an internal, non-serviceable part of the high pressure lock-off (HPL) solenoid valve. On Type 4 fuel tanks the PRD is externally threaded into an open port of the HPL solenoid valve. The PRD port is not controlled by the HPL solenoid valve and is directly open to the internal tank pressure. The CNG fuel tank must be completely vented prior to removing the external PRD. The external PRD should be inspected regularly. Refer to Fuel Tank Inspection (Type 2 Tank) .
Fill Valve and Fill Line
The fill valve receives fuel from the fill nozzle at the CNG dispensing station. The fill valve seals to the dispensing nozzle with an O-ring. The O-ring must be inspected and replaced if missing or damaged prior to re-fueling. The fill valve contains an internal 380 micron filter element designed to trap contaminants. This filter must be periodically inspected and cleaned. Refer to Fill Valve Filter Replacement for filter inspection and cleaning procedures. The fill valve mounting location varies with vehicle model. Refer to the owner's manual supplement for fill valve location and fuel tank filling procedures. The fill line is constructed of stainless steel line. The fill line connects the fill valve to the fuel tank and is sealed to the fuel tank with an O-ring.
Fill Line Union Check Valve
The fill line is equipped with a check valve. In the event of fill valve leakage, the check valve is designed to minimize the amount of CNG fuel leakage. The check valve must be installed with the flow direction arrow pointed toward the high pressure lock-off solenoid.
High Pressure Lock-Off (HPL) Solenoid
The HPL is a normally closed, solenoid valve. The HPL solenoid and a low pressure lock-off (LPL) solenoid in the fuel line prevent fuel flow. The powertrain control module (PCM) commands ONLY the HPL open for 1 second at EVERY ignition ON in order to prime the CNG fuel system. The CNG prime pulse charges the fuel line which allows the fuel tank pressure (FTP) sensor to monitor the amount of fuel pressure in the system. The PCM commands BOTH the HPL and the LPL open when engine RPM indicates that the engine is cranking or running on CNG.
Fuel Tank Pressure (FTP) Sensor
The FTP sensor is a pressure transducer. The fuel injector control module (FICM) supplies about 5 volts on the FTP reference circuit. The FICM also supplies a signal and ground circuit to the FTP. When the fuel tanks are full (high pressure) a high voltage signal will be monitored by the FICM. The FTP sensor is threaded into the fuel tank HPL solenoid. The FTP sensor voltage is sent to the PCM through a PWM circuit. The volume of CNG will vary with temperature and pressure. Accurate CNG fuel level cannot be determined by pressure only. In order to compensate for the different volume factors a fuel tank temperature (FTT) sensor is mounted within the HPL. The PCM performs a calculation on the fuel tank pressure vs the in-tank temperature. The PCM will then display the temperature corrected CNG fuel level. The CNG FTP sensor should not be confused with the gasoline fuel tank pressure (FTP) sensor that is utilized for Evaporate (EVAP) emissions monitoring.
Fuel Tank Temperature (FTT) Sensor
The FTT sensor is a thermistor mounted inside the HPL and is not serviceable separately from the HPL. The FTT thermistor has high resistance when cold and low resistance when hot. The FICM supplies about 5 volts to the FTT sensor signal circuit. When the FTT sensor is cold its resistance is high and the signal voltage is high. As the FTT sensor warms and resistance drops, less signal voltage is monitored by the FICM. The FTT sensor voltage is sent to the PCM through a PWM circuit. The volume of CNG will vary with temperature and pressure. Accurate CNG fuel level cannot be determined by pressure only. In order to compensate for the different volume factors the fuel tank temperature (FTT) sensor is mounted within the HPL. The PCM performs a calculation on the fuel tank pressure vs the in-tank temperature. The PCM will then display the temperature corrected fuel level.
High Pressure Line
The high pressure line is stainless steel tubing with matching high pressure O-ring face seal (ORFS) fittings. The individual tubes are pre-formed with fittings installed. All O-ring face seal fittings use nitrite rubber O-rings and must be replaced with the correct replacement part whenever a line is opened.
When installing pipe thread fittings DO NOT use Teflon® tape. Tape fragments could lodge in a regulator and allow fuel pressure to exceed specified levels. The use of pipe sealant with Teflon® is required.
Intermediate Pressure Fuel Hose
The intermediate pressure fuel hose assembly is a unique 2-piece stainless steel braided hose and is designed to isolate AF components from vibration.
Coalescing CNG Fuel Filter
The coalescing CNG fuel filter is located between the high pressure lock-off solenoid and the high pressure regulator. The coalescing filter housing contains a 6-micron filter element as well as a drain fitting. The coalescing filter is designed to trap contaminates and liquids that may damage the gaseous fuel injectors. This filter must be periodically inspected, drained and replaced.
Fuel Metering Components
The alternative fuels metering system consists of the following components
- High Pressure Regulator (HPR)
- Low Pressure Lock-Off (LPL) Solenoid
- Intermediate Pressure Regulator (IPR)
- CNG Fuel Injectors
- Fuel Rail Pressure Sensor
- Fuel Rail Temperature Sensor
High Pressure Regulator (HPR)
The HPR is supplied with fuel from the CNG fuel tank at up to 24,821 kPa (3,600 psi) through high pressure stainless steel lines. The HPR reduces fuel pressure to between 758-1,448 kPa (110-210 psi). The outlet of the HPR is the Intermediate pressure stage. Fuel flows out of the HPR and into the low pressure lock-off (LPL) solenoid. The pressure drop within the regulator causes fuel temperature to drop. In order to prevent HPR freeze-up, the HPR is connected to the vehicle engine cooling system. The HPR contains an over-pressure relief device (PRD) which will not allow pressure above 1,896 kPa (275 psi) on the output stage of the HPR. The PRD is removable in order to allow the installation of a pressure gage for diagnostic purposes. The HPR has an internal, serviceable 40-micron filter. This filter must be serviced periodically. Refer to High Pressure Regulator (HPR) Filter Replacement for replacement procedures.
Low Pressure Lock-Off (LPL) solenoid
The LPL is a normally closed, solenoid valve. The LPL is mounted in the Intermediate pressure line. The PCM controls LPL solenoid operation. The PCM energizes the LPL solenoid only when engine cranking or running is detected. Anytime the engine is stopped the PCM de-energizes the LPL solenoid in order to stop fuel flow. The PCM operates the LPL and the high pressure lock-off (HPL) solenoid at the same time except at ignition ON. During ignition ON only the HPL is opened, while the LPL remains closed, in order to charge the fuel system with CNG. The LPL is supplied fuel from the HPR with fuel pressure between 758-1,448 kPa (110-210 psi). The outlet of the LPL supplies the intermediate pressure regulator (IPR) with fuel.
Intermediate Pressure Regulator (IPR)
Fuel enters the IPR at the intermediate stage pressure of 758-1,448 kPa (110-210 psi). The IPR reduces the fuel pressure down to about 276 kPa (40 psi). The fuel exits the IPR and flows to the CNG fuel rails. The IPR is equipped with a Schrader valve for testing the inlet pressure. Refer to Fuel System Diagnosis for pressure checking procedures.
Gaseous Fuel Injectors
The gaseous fuel injectors are pulse-width modulated and sequentially fired. The injector voltage is supplied by an injector relay. The FICM controls the ground path.
Fuel Rail Pressure Sensor
The fuel rail pressure (FRP) sensor is a pressure transducer. The PCM supplies about 5 volts on the FRP sensor reference circuit. The PCM also supplies a signal and ground circuit to the FRP sensor. When fuel pressure is high the signal voltage is high. The FRP signal is used by the PCM for fuel trim adjustment.
Fuel Rail Temperature Sensor
The fuel rail temperature (FRT) sensor is a thermistor. The FRT thermistor has high resistance when cold and low resistance when hot. The FICM supplies about 5 volts to the FRT sensor signal circuit. When the FRT sensor is cold its resistance is high and the signal voltage is high. As the FRT sensor warms and resistance drops, less signal voltage is monitored by the FICM. The FRT sensor voltage is sent to the PCM through a PWM circuit. The FRT signal is used by the PCM for fuel trim adjustment.
60 Day Cycle
It is recommended that every 60 days the vehicle be cycled between CNG and gasoline. This ensures the gasoline fuel system stays in good working condition and also accommodates for seasonal changes in gasoline formulation. Perform the following steps every 60 days.
- With the vehicle operating on CNG check and fill the gasoline level.
- Operate the vehicle until the CNG fuel tank is empty and the vehicle switches over to gasoline operation.
- Operate the vehicle until the gasoline tank is near empty.
- Refill both fuel tanks.
- The vehicle will switch-over to CNG operation.
- Repeat procedure in 60 days.
Fuel Indicator Message
The PCM indicates which fuel system is in operation by sending a serial data message to the instrument panel. The driver information message center is contained within the instrument panel. The PCM controls the operation of the alternative fuels related messages. The messages momentarily indicate which fuel system is in operation during engine start-up. A message indicating which fuel level is being shown will also be momentarily displayed when the vehicle operator presses the fuel gage select switch.