Vehicles may be converted in California if they are converted according to the California Air Resources Board's Executive Orders. The Executive Orders (EOs) fall into two groups: 1993 & older vehicles and 1994 & newer vehicles.

All 1976 & newer gasoline vehicles in CA must use CARB-approved LPG or CNG equipment during a conversion. For models 1993 & older, the EOs are summarized in Document A-93-551, which are pretty flexible and easy to follow. An EO requires only that the components be sized properly for the engine and for each other. Relevant emission controls (catalyst, feedback, etc) must be retained but does not limit specific components to specific engine(s)/families. A common EO for conversion is "B-4-38", which uses Impco components.

Since CARB EOs apply to 1976 & newer vehicles, pre-1976 vehicles have much more flexibility with regard to the fuel systems available for installation. If you are interested in using an alternative fuel, your options are completely open (provided you follow NFPA 58 or NPFA 52) with regard to the type of fuel system you can install. LPG or CNG injection is definitely a possibililty for these vehicles.

For vehicles 1994 & newer, the EOs are summarized in ALTERNATIVE FUEL RETROFIT SYSTEMS CERTIFIED BY THE AIR RESOURCES BOARD. These EOs are issued by engine family and are more difficult to implement. These will usually be issued for common truck/fleet engines (GM, Cummins, Caterpillar, etc).

For applications that do not already have an EO or if you want to use different components than are already approved, you must apply for a new EO. The certification process for an EO application is detailed in the Final Regulatory Order. This is an expensive and onerous process that should not be undertaken lightly.

(The information in this article was very generously provided by A. Bugrov of the Central Coast Clean Cities Coalition).