GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Savana (CNG) 🢒 Engine 🢒 Engine Controls - 5.0L and 5.7L 🢒 Poor Fuel Fill Quality

Checks

Action

DEFINITION 1: Fuel filling time, as measured against previous filling time, is noticeably longer than expected.

DEFINITION 2: The fuel tanks only appear to fill halfway.

Fuel System Checks

Inspect for the following conditions:

    • A contaminated or clogged fill valve filter. A service interval is not specified for the fill valve filter. The fill valve filter's condition depends on fuel quality. Use of CNG with excessive amounts of contaminants or compressor oil will increase the frequency of service. Service if necessary.
    • A fill line union check valve that is restricted or improperly installed. The check valve flow direction arrow should point towards the fuel tank.

       Important: The customer may comment that one fuel tank does not appear to fill. An inoperative high pressure lock-off (HPL) solenoid valve will allow a tank to fill but will not allow it to empty.

    • Test for operation of BOTH fuel tank HPL solenoid valves by performing the following:
        1. Start and idle the engine on CNG.
        2. Observe the fuel gage as you disconnect the front tank HPL.
        3. Leave the front tank HPL disconnected for about 2 minutes.
        4. Reconnect the front tank HPL.
        5. Ensure the engine is still operating on CNG.
        6. Observe the fuel gage as you disconnect the rear tank HPL.
        7. Leave the rear tank HPL disconnected for about 2 minutes.
        8. If the disconnection of either HPL caused the fuel gage to drop or caused the engine to switch-over to gasoline operation, test for the following:
       - A closed HPL manual shut-off valve.
       - A lack of power or ground at the HPL connector when commanded ON.
       - An open or shorted HPL solenoid. Replace the HPL as necessary. Refer to High Pressure Lock-Off Solenoid Replacement