Fuel System Checks

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

Check the following items:

Check for proper fuel system pressures. See FUEL SYSTEMS (CNG) in SYSTEM & COMPONENT TESTS - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE article.
Check for proper operation of the CNG fuel injectors. See FUEL INJECTOR COIL TEST , FUEL INJECTOR BALANCE TEST WITH SPECIAL TOOL and FUEL INJECTOR BALANCE TEST WITH TECH 2 under FUEL SYSTEMS (CNG) in SYSTEM & COMPONENT TESTS - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE article.
Check the high and low pressure lock-off valves/circuits for proper operation.