Engine - Hard Cold Starting and Performance
GROUP23
NUMBER
26
ISSUING DEPARTMENT
Technical Support
CAR MARKET
U.S.
DATE
August, 1992
TITLE
LOW RVP FUEL
REFERENCE BULLETINS:
You may be experiencing an increase in customer complaints related to cold starting and/or cold drive away performance. These problems may be related to the use of low volatility fuels which are now in use during the summer months in the U.S.
In an effort to reduce air pollution, The Clean Air Act of 1990 now requires the use of lower volatility or vapor pressure fuels from June 1 to September 15 (in some areas beginning May 1). While some areas have already required the use of low vapor fuels, many areas are using these fuels for the first time.
To accommodate these requirements, the vapor pressure of gasoline is reduced to either 7.8 PSIG for warm and/or poor air quality areas, or 9.0 PSIG for the remaining areas. See map. Vapor pressure may also be referred to in the industry by its method for measuring vapor pressure "Reid Vapor Pressure" or just "RVP."
Complaints attributable to low vapor pressure usually are: hard cold starting, cold start drive away hesitation, and cold start-up and stall. Generally these conditions will diminish as the engine is warmed up.
It is important that the customer realize the existence of these fuels in the market place and their contribution to improved clean air quality.
Before a prolonged diagnosis or repair is attempted to solve the complaints described above, the customer should first be asked to change fuel brands or fuel stations. This would eliminate the possibility of an individual and/or inferior fuel batch variations.
Poorly maintained vehicles or vehicles with pre-existing problems can exhibit symptoms similar to those described above (for example fouled fuel injectors or heavily deposited intake valves, etc.).