Running Losses: Notes

The fuel system is the largest contributor to running losses. For example:

• An electric fuel pump cycles the entire contents of the fuel tank through the fuel rail and back to the tank twice every hour.
• The fuel absorbs the heat of the engine compartment as it continually cycles through the fuel rail and raises to a temperature as high as 158°F.
• The added heat causes the gasoline to vaporize increasing the amount of HC in the fuel system.
• If a leak develops in the system or when the fuel cap is removed at the gas station the additional gasoline vapors generated by the heat of the engine compartment only add to the escaped VOC.