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Note: There are two different fuel filter systems. In system 1, the fuel filter is located on the engine, under the engine cover. In system 2, the fuel filter is located to the left in the engine compartment, on the strut tower. Special tools, testers and auxiliary items required Suction pump VAS 5226 Remove engine cover Removing: Upper engine cover, removing and installing . Remove plug – arrow – from fuel filter housing water drain connector. Extract diesel fuel via water drain connection located on the side of the fuel filter housing – arrow – using V.A.G 1390 and V.A.G 1390/1 . Seal off oil plug again and tighten to 3 Nm. Remove line connectors for fuel lines Remove screws – arrows – along with connection lines to fuel filter housing Removing fuel filter cover: Remove screws – arrow – for fuel filter housing and remove cover Remove fuel filters – 3 – from cover – 1 – Note: Observe waste disposal regulations! Installing: Install new fuel filters – 3 – and replace seal – 2 – Install fuel filter cover – 1 – . Tighten screws – arrows – for fuel filter cover (8 Nm) Install line connectors for fuel lines. Note: Replace sealing ring between fuel filter covers and line unions for fuel hoses. Tighten bolts – arrows – to 8 Nm. Fuel system, bleeding In order to ensure engine starts immediately after changing fuel filter, fuel system must be bled with diagnostic tester. Connect diagnostic tester Switch ignition on. Select “Guided Functions” . Perform vehicle identification. Diagnostic testing unit, connecting .

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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

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IMPORTANT: Inspect the fuel tank internally and clean the fuel tank if you find a restricted fuel filter. 1. Relieve the fuel system pressure. Refer to the Fuel Pressure Relief Procedure. 2. Raise the vehicle. Refer to Lifting and Jacking the Vehicle. 3. Clean all the fuel filter connections and the surrounding areas before disconnecting the fuel pipes in order to avoid possible contamination of the fuel system. 4. Disconnect the threaded fittings (1, 2) from the fuel filter. 5. Remove the fuel filter bracket bolt (4). 6. Cap the fuel pipes in order to prevent possible fuel system contamination. 7. Slide the fuel filter from the bracket. 8. Inspect the fuel pipe O-rings for cuts, nicks, swelling, or distortion. Replace the O-rings if necessary. INSTALLATION PROCEDURE 1. Slide the fuel filter into the bracket. 2. Remove the caps from the fuel pipes. NOTE: Refer to Fastener Notice in Service Precautions. 3. Connect the threaded fittings (1, 2) to the fuel filter. Tighten ^ Tighten the fittings to 25 N.m (18 lb ft)Tighten the fuel filter bracket bolt (4), to 12 N.m (106 lb in). 4. Lower the vehicle. 5. Tighten the fuel filler cap. 6. Connect the negative battery cable. 7. Use the following procedure in order to Inspect for leaks. 7.1. Turn ON the ignition, with the engine OFF, for 2 seconds. 7.2. Turn OFF the ignition for 10 seconds. 7.3. Turn ON the ignition, with the engine OFF. 7.4. Inspect for fuel leaks. 7.5. Install the engine sight shield

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1. Remove the fuel sender assembly. Refer to Fuel Sender Assembly Replacement. 2. 3. 4. 5. 6. Disconnect the fuel pump electrical connector. Remove the retaining clip from the fuel level sensor connector. Disconnect the electrical connector from under the fuel sender cover. Remove the sensor retaining clip. Squeeze the locking tangs and remove the fuel level sensor (3). Installation Procedure 1. 2. 3. 4. Install the fuel level sensor (3). Install the sensor retaining clip. Connect the electrical connector to the fuel level sensor. Install the retaining clip to the fuel level sensor electrical connector. 5. Connect the fuel pump electrical connector. 6. Install the fuel sender assembly. Refer to Fuel Sender Assembly Replacement. FUEL SENDER ASSEMBLY REPLACEMENT Tools Required J 45722 Fuel Tank Sending Unit Wrench. See Special Tools. Removal Procedure 1. Remove the fuel tank. Refer to Fuel Tank Replacement (TrailBlazer EXT, Envoy XL, Envoy XUV) or Fuel Tank Replacement (TrailBlazer, Envoy, Rainier).

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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.