Removal & Installation (CNG)

WARNING: This page is about a different car, the 2003 GMC Savana and 2003 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION: Natural gas is highly flammable. In order to reduce the risk of fire and personal injury, keep sparks, flames, and smoking materials away from the vehicle while you perform the Compressed Natural Gas (CNG) fuel system service.

CAUTION: Natural gas is stored under high pressure. If a leak occurs, the high pressure could cause a personal injury. In order to prevent Compressed Natural Gas (CNG) fuel leaks, always replace the CNG fuel system "O" rings during service.

NOTE: Before removal, clean the fuel rail assemblies with a spray type engine cleaner, GM X-30A or equivalent, if necessary. Follow the package instructions. DO NOT soak fuel rails in liquid cleaning solvent.

NOTE: Remove the fuel rail assembly carefully in order to prevent damage to the injector electrical connector terminals and the injector spray tips.

NOTE: Use NEW "O" rings upon installation. Lubricate all "O" rings with petroleum jelly or equivalent before installation.

NOTE: Numbers in parenthesis refer to numbers in illustration.

Relieve the CNG fuel system pressure. See FUEL SYSTEM PRESSURE RELEASE . Disconnect the negative battery cable. Remove the engine cover.

CAUTION: Identify the injector connectors to their corresponding engine cylinder to ensure correct sequential injector firing order after reassembly.

Disconnect the CNG fuel lines (7, 8 and 10) from the fuel rails. See Figure. Disconnect the fuel rail temperature and pressure sensor electrical connectors (3 and 4). Disconnect the low pressure lock-off solenoid connector. Disconnect the eight CNG fuel injector electrical connectors (2 and 12).
Disconnect the accelerator control cable and the cruise control cable from the cable bracket. Disconnect the cruise control cable engine-end fitting from the stud on the throttle lever, if equipped. Disconnect the accelerator control cable and the cruise control cable from the throttle body.
Remove the upper engine wire harness retainer nut. See Figure. Set the upper engine wire harness aside. Remove the right fuel rail attaching bolts.
Support the fuel rail after the fuel rail is removed in order to avoid damaging the fuel rail components. Cap the fittings and plug the holes when servicing the fuel system in order to prevent dirt and other contaminants from entering open pipes and passages. Remove the left fuel rail attaching bolts. Remove the CNG fuel rail.
Remove the injector (7) retainer bolt and clip (10). See Figure. Remove the injector from the fuel rail with a pulling a twisting motion. Repeat steps for the remaining fuel injectors. Remove the fuel rail pressure sensor (13) and discard the O-ring. See FUEL RAIL PRESSURE SENSOR under SENSORS & SWITCHES.
Remove the fuel rail temperature sensor (11) and discard the "O" ring. See FUEL RAIL TEMPERATURE SENSOR under SENSORS & SWITCHES. Remove the low pressure lock-off solenoid (2) mounting screws (1) and discard the O-ring (12).
To install reverse removal procedure. Tighten all fasteners to specification. See TORQUE SPECIFICATIONS . Lubricate the NEW fuel injector lower "O" ring seals with clean engine oil. Install the NEW "O" ring seals to the end of each injector.
Apply a 0.020" (5 mm) band of (GM P/N 1234382) threadlock, or equivalent, to the threads of all of the fuel rail attaching studs.
Connect the CNG fuel inlet line using a NEW copper sealing washer. Connect the CNG fuel crossover line using NEW copper sealing washers.
Start the vehicle and inspect for CNG fuel leaks at the serviced fittings with the Ultrasonic Leak Detector (J 45878) or an equivalent leak detector. With a scan tool command a switch-over to gasoline and inspect for gasoline fuel leaks. Install the engine cover.