F 250 4WD Super Duty V10-6.8L VIN Z CNG (2003)
On-Board Refueling Vapor Recovery Evaporative Emission System
The basic elements forming the ORVR system (Figure 107), (Figure 108) and (Figure 109) operation are as follows when fuel is dispensed:
1. The fuel filler pipe forms a seal to prevent vapors from escaping the fuel tank, while liquid is entering the fuel tank (liquid in the one inch
diameter tube blocks vapors from rushing back up the fuel filler pipe).
2. A fuel vapor control valve controls the flow of vapors out of the fuel tank (valve closes when liquid level reaches a height associated with
the fuel tank usable capacity). This valve accomplishes the following:
a. Limits the total amount of fuel that can be dispensed into the fuel tank.
b. Prevents liquid gasoline from exiting the fuel tank when submerged (and also when tipped well beyond a horizontal plane as part of the
vehicle roll-over protection in road accidents).
c. Minimizes vapor flow resistance during anticipated refueling conditions.
3. Fuel vapor tubing connects the fuel vapor control valve to the EVAP canister. This routes the fuel tank vapors (displaced by the incoming
liquid) to the EVAP canister.
4. A check valve in the bottom of the fuel filler pipe prevents liquid from rushing back up the fuel filler pipe during the liquid flow variations
associated with the filler nozzle shut-off.
Between refueling events, the EVAP canister is purged with fresh air so that it may be used again to store vapors accumulated during engine soaks
or subsequent refueling events. The vapors drawn off of the carbon in the EVAP canister are consumed in the engine.
Refer to Evaporative Emissions System for information on the following Evaporative Emission System components: liquid/vapor fuel
discriminator, fuel filler pipe check valve, fill limit valve assembly, fill limit vent valve assembly, fuel filler pipe flapper valve, fuel vapor control
valve (fuel tank mounted), ORVR T-connector assembly and EVAP canister.
