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WARNING: Begin fuel system trouble shooting and diagnosis with fuel system pressure test. Relieve fuel system pressure before disconnecting any components or installing fuel pressure gauge. TBI 1. Turn ignition off for 10 seconds. Turn ignition on, and listen at fuel tank for fuel pump operation. Pump should run 2 seconds (20 seconds on models with fuel module). If fuel pump runs, go to next step. If fuel pump does not run, go to step 7). 2. If fuel pump runs, turn ignition off. Verify fuel tank has fuel. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF . Remove air cleaner, and plug air cleaner vacuum ports (if equipped). Disconnect fuel line between throttle body and fuel filter. Install Fuel Pressure Gauge (J-29658A) and Adapter (J- 2968A-85) between steel fuel line and flexible hose, ahead of in-line fuel filter. 3. Turn ignition on, and note reading on pressure gauge. If fuel pressure is 9-13 psi (.63-.91 kg/cm2 ), no problems exist. If pressure is less than 9 psi (.63 kg/cm2 ), go to step 5). If pressure is greater than 13 psi (.91 kg/cm2 ), turn ignition off, and bleed fuel pressure. Disconnect fuel return line downstream of pressure gauge. Insert return line into a gasoline container. 4. Turn ignition on. If pressure is now 9-13 psi (.63-.91 kg/cm2 ), correct restriction in fuel return line between disconnected point and fuel tank. If fuel pressure is greater than 13 psi (.91 kg/cm2 ), check for restricted return line (including fuel filter) downstream of pressure gauge. If no restrictions are present, replace fuel pressure regulator (TBI 700) or fuel meter cover/pressure regulator (TBI 220). 5. Check for restricted line between in-tank fuel pump and pressure regulator. If fuel line is okay, disconnect injector connector. Turn ignition on. Gradually pinch fuel pressure gauge outlet hose. Note pressure. CAUTION: DO NOT pinch off fuel return line completely. DO NOT allow fuel pressure build-up to exceed specification, as damage to fuel pressure regulator may occur. 6. If pressure is greater than 13 psi (.91 kg/cm2 ), replace fuel pressure regulator (TBI 700) or fuel meter cover/pressure regulator (TBI 220). If pressure is less than 9 psi (.63 kg/cm2 ), check for faulty fuel pump or incorrect part. Check fuel pump coupling hose and pump inlet filter in fuel tank. On models with dual fuel tanks, check for faulty fuel tank selector valve and meter switch.

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NOTE: 1. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE . Install a fuel pressure gauge between fuel pressure regulator and fuel distributor pipe. See Fig. 1 . Bleed air from fuel line going to pressure gauge. 2. Unplug fuel pressure regulator Vacuum Switching Valve (VSV) connector on right side fender skirt. This is a 4-wire connector with Black and Blue wires in harness. PCM controls VSV to cut vacuum to fuel pressure regulator during hot engine starts. 3. Start engine and measure fuel pressure at idle. Disconnect fuel pressure regulator vacuum hose. Note fuel pressure at idle with vacuum hose disconnected (no vacuum). Fuel pressure should be 42 psi (3.0 kg/cm2 ). See FUEL PUMP PERFORMANCE . 4. If fuel pump pressure is low, check for fuel leaks, restrictions in intake side of fuel pump, leaking injectors, faulty pressure regulator or faulty fuel pump. If fuel pressure is high, check for restrictions in return line to tank or faulty pressure regulator. If pressure does not change when pressure regulator is disconnected, replace pressure regulator. 5. Reconnect pressure regulator vacuum hose and check fuel pressure (with vacuum). Fuel pressure should be 35 psi (2.4 kg/cm2 ). Apply battery voltage to VSV connector Blue wire terminal, and ground Black wire terminal (with vacuum). See Fig. 2 . Fuel pressure gauge should read about 42 psi (3.0 kg/cm2 ). If fuel pressure is not within specification, check for defective VSV. 6. Disconnect and plug vacuum hose from fuel pressure regulator. Stop engine and ensure fuel pressure remains greater than 35 psi (2.4 kg/cm2 ) for 4 minutes after engine stops. 7. If pressure drops, check for leaking injectors, faulty pressure regulator or bad check valve in fuel pump. If engine does not start, by-pass fuel pump relay to check for fuel pressure. Remove fuel pump relay from underhood fuse/relay box. Connect a fused jumper wire between terminals No. 1 and 3 of fuel pump relay connector in fuse block. See Fig. 3 and Fig. 4 . 8. If fuel pump does not operate, check for battery voltage to terminal No. 3. If battery voltage is present, check for open in fuel pump circuit. If fuel pump operates with jumper wire installed, check fuel pump relay and relay energizing circuit. Repair as necessary. Begin basic fuel system diagnosis with testing fuel pressure.

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Customer may report that the vehicle is hard to fill with fuel or that the fuel pump nozzle shuts off repeatedly while trying to fill vehicle. This customer complaint can occur due to a number of different causes. The fuel tank is the least likely cause of this condition. The following Diagnostic procedure can be used to diagnose the issues. DIAGNOSIS: 1. Is the vehicle a LX/LE/LC/L2? a. Yes >> proceed to Step #2 b. No >> proceed to Step #4 2. Idle the vehicle 60 to 90 seconds upon stopping. 3. Does tank refill properly? a. No >> proceed to Step #4 b. Yes >> Inform the customer to idle the vehicle for 60 to 90 seconds upon stopping if vehicle was driven aggressively. This is due to the fact that on the LX/LE/LC/L2 the fuel tank is a unique saddle tank design and needs 30 to 60 seconds while the engine is running to level the fuel in both half’s of the fuel tank. Allowing the vehicle to idle for this amount of time will let the fuel pump transfer fuel to the left side tank, opening the control valve and allowing normal fuel filling. 4. Disconnect the vapor recirculation tube at the fuel tank. 5. Attempt to refill fuel tank. 6. Does tank refill properly? a. Yes >> Proceed to Step #7 b. No>> Proceed to Step #11. 7. Reconnect the vapor recirculation tube at the fuel tank. 8. Disconnect the other end of the vapor recirculation tube at the fuel filler tube. 9. Attempt to refill fuel tank. 10. Does tank refill properly? a. Yes >> Replace fuel filler tube. b. No >> Replace the vapor recirculation tube. 11. Disconnect the control valve to EVAP canister tube at the fuel tank. -3- 12. Reconnect the vapor recirculation tube at the fuel tank. 13. Does tank refill properly? a. No >> Replace Fuel Tank. b. Yes >> Proceed to Step #14. 14. Reconnect the control valve to EVAP canister tube at the fuel tank. 15. Disconnect the control valve to EVAP canister tube at the EVAP canister. 16. Attempt to refill fuel tank. 17. Does tank refill properly? a. Yes >> Blockage is in the EVAP Canister, or ESIM, or Clean air hose (ESIM vent hose), or filter. Diagnose appropriately. b. No >> Replace the control valve to EVAP canister tube.

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FUEL SYSTEM PRESSURE RELEASE NOTE: 1. Loosen fuel tank filler cap to relieve tank pressure. Remove fuel pump relay from underhood fuse/relay box. Start and operate engine until it stalls. Crank engine an additional 30 seconds. 2. Loosen hose clamp of fuel line on side of pressure regulator, coming from fuel line inlet distributor pipe. Cover fuel hose with a shop towel, and slowly pull hose from pressure regulator to relieve fuel pressure. When fuel stops leaking, reinstall hose and clamp. FUEL PRESSURE & FUEL PUMP RELAY TEST NOTE: Fuel Pressure 1. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELEASE . Attach Fuel Pressure Gauge Set (J-34730-1 ) and Adapter (J-35957-1 ) to Schrader fitting on fuel rail. Disconnect pressure regulator vacuum hose. Turn ignition on. Allow fuel pump to run for about 2 seconds. 2. Fuel system pressure should be about 41-46 psi (2.8-3.2 kg/cm2 ). See FUEL PUMP PERFORMANCE . Start engine and check for leaks. Connect pressure regulator vacuum hose. If engine will not start, the fuel pump relay can be by-passed. Also see appropriate CHART A-3 – ENGINE CRANKS BUT WILL NOT RUN under TROUBLE SHOOTING CHARTS. With engine idling, fuel pressure should be 25-30 psi (1.8-2.1 kg/cm2 ). NOTE: Fuel pump relay is located in engine compartment fuse/relay box. Begin basic fuel system diagnosis with testing fuel pressure. To test the fuel pump relay circuit, proceed to CHART A-5 – FUEL PUMP RELAY CIRCUIT under TROUBLE SHOOTING CHARTS. Fuel Pump Relay 1. ECM supplies power to relay as long as ECM receives ignition reference signals or starter crank signal. To run fuel pump without starting engine, remove relay and jumper terminals No. 2 and 4. See Fig. 5 and Fig. 6 . 2. To test relay, use jumper wires to ground terminal No. 4 of relay and apply battery voltage to terminal No. 2 of relay. Using ohmmeter, check for continuity between relay terminals No. 1 and 3. If continuity is not present, replace relay.

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Fuel Charging and Controls The fuel charging and controls system consists of: fuel pressure regulator (9C968) fuel injection supply manifold (9F792) fuel injectors (9F593) fuel shut off valve solenoid (9D278) fuel pressure relief valve (9H321) injection pressure sensor engine fuel temperature sensor fuel charging wiring harness Component Location Fuel Pressure Regulator The fuel pressure regulator is located on the inside of the LH frame rail just forward of the transmission support crossmember. It is part of an assembly that includes the coalescer/filter. The fuel pressure regulator reduces the line pressure from tank pressure 20685 kPa (3000 psi) to line pressure 655 kPa (95 psi). Heating/Defrosting—Natural Gas Vehicle Fuel pressure regulator heating is provided by two 3/8-inch taps from the existing heater supply and return hoses on the RH rear of the engine. Two high-temperature 3/8-inch ID heater hoses (packaged with the front low-pressure fuel line) are used to connect the fuel pressure regulator to the tap points on the engine heater hoses. Refer to the Line — Low Pressure Fuel procedure in Section 310-01B for fuel pressure regulator heater hose replacement. Fuel Pressure Regulator Heater Hoses Fuel Injection Supply Manifold The fuel injection supply manifold delivers high-pressure fuel from the vehicle fuel supply line to the fuel injectors. The fuel injection supply manifold consists of the following: a tubular fuel rail eight fuel injector connectors a fuel pressure relief valve a fuel shut off valve solenoid mounting attachments which locate the fuel injection supply manifold and provide fuel injector retention. a fuel inlet connection which has a push-connect fitting an injection pressure sensor an engine fuel temperature sensor Fuel Injection Supply Manifold Fuel Injectors The natural gas fuel injectors are electro-mechanical devices that meter fuel delivered to the engine. The natural gas fuel injectors are mounted in the lower intake manifold (9424) and are positioned so that their tips direct fuel just ahead of the engine intake valves (6507). The natural gas fuel injector bodies consist of a solenoid and a needle and valve assembly. Natural gas fuel injectors can be identified by an aqua cap on the injector body. Fuel Shutoff Valve Solenoid The fuel shut off valve solenoid seals the upstream fuel pressure from entering the fuel injection supply manifold when the engine is not running. The fuel shut off valve solenoid is open only when it is activated by the solenoid valve (fuel pump) relay. Fuel Pressure Relief Valve The fuel pressure relief valve is located on the fuel injection supply manifold, and is used to relieve fuel system pressure from the fuel delivery system. Injection Pressure Sensor The injection pressure sensor is located on the fuel injection supply manifold, and is used to provide a signal to the powertrain control module (PCM) (12A650) that is proportional to pressure in the fuel injection supply manifold. Engine Fuel Temperature Sensor The engine fuel temperature sensor is located on the fuel injection supply manifold, and is used to provide a signal to the powertrain control module that indicates the temperature of the fuel in the fuel injection supply manifold. Fuel Charging Wiring The fuel charging wiring is a single harness that includes electrical connectors for the fuel injectors, ignition coils and various sensors, valves and senders that monitor all engine functions. Fuel Charging Wiring