Alternate Fuel Notes

I have found many CNG, LPG and Dual-Fuel systems to be very sensitive to dirty air filters. As the air filters get dirty, Carbon Monoxide (CO) levels can increase by as much as 3%. Also, keep in mind that different brands of new air filters may affect the flow of the system, sometimes so much that the fuel mixture may change by as much as 1.5%. Be sure to check the mixture after changing the air filter and/or brand.

Sometimes people remove all the emissions equipment from their vehicle after they install an alternate fuel system. Then when they are told they need to reinstall all the emissions equipment to be legal, they just don't seem to understand why they need it. Alternate fueled vehicles do pollute, just slightly less than gasoline powered vehicles. Many systems have connections to maintain the computer controls. Some manufacturers may be allowed to remove or disconnect some of the computer controls. The modifications allowed depend on how the alternate fuel systems were configured when they were submitted to the California Air Resources Board for approval.

When running an emissions test on an alternate-fuel vehicle, the best source of inspection information is the underhood label. When the fuel systems are installed the installer is required to place an underhood label which provides much of the information needed for the emissions inspection such as ignition timing, mixture adjustment procedure, etc. Many alternate fuel systems provide a tag or have embossed on their component the location of adjustment screws, etc.

As of January 1, 1994 the State of California required all retrofitted alternate fuel systems to go to a State contracted "Referee" facility for inspection and certification. If the vehicle configuration passes inspection, a metal label is placed on the vehicle by the "Referee" facility. From that point on the vehicle may be inspected by a Smog Check station.

The Editor, William Sullivan is an automotive engineer.