Evaporative Emissions

WARNING: This page is about a different car, the 2005 Ford RV Cutaway, 2005 Ford Econoline, 2005 Ford E450 Super Duty, and 2005 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Identifying Evaporative Emission System Components - Midship Fuel Tank

Courtesy of FORD MOTOR CO.

Fig 2: Identifying Evaporative Emission System Components - Aft-of-Axle Fuel Tank

Courtesy of FORD MOTOR CO.

The evaporative emission (EVAP) system:

prevents hydrocarbon emissions from reaching the atmosphere.
stores fuel vapors in the evaporative emissions (EVAP) canister that are generated during vehicle operation or hot soak, until they can be consumed by the engine during normal engine operation.
routes the stored fuel vapors to the engine during engine operation.
is controlled by the powertrain control module (PCM) which uses various sensor inputs to calculate the desired amount of EVAP purge flow. The PCM regulates the purge flow, induced by the application of intake manifold vacuum, by varying the duty cycle applied to the canister purge valve.
has an evaporative emission test port for test purposes.

The fuel vapors are routed:

from the fuel tank through the fuel vapor vent valves.
to the evaporative emissions (EVAP) canister through a vapor line.
to the engine when the evaporative emission (EVAP) canister purge valve is opened by the powertrain control module (PCM).

The fuel tank pressure (FTP) sensor:

monitors the pressure levels in the fuel tank.
communicates the pressure reading to the PCM during the OBD II leak test.

The evaporative emissions (EVAP) canister:

is located along the LH frame rail for vehicles with rear fuel tanks or on the rear crossmember for vehicles with a midship fuel tank.
contains activated carbon.
stores fuel vapors.

The fuel tank filler cap:

relieves system vacuum below 3.5 kPa (15.09 inches H₂ O).

The canister vent solenoid:

is normally open.
seals the EVAP system for the OBD II leak and pressure tests.
is mounted to the EVAP canister.
is repaired as a separate item.

The evaporative emission canister purge valve:

is normally closed.
regulates the purging of the EVAP canister.
is controlled by the powertrain control module (PCM).

The evaporative emission (EVAP) system test port:

is located near the EVAP canister purge valve.
is used to connect the Evaporative Emission System Leak Tester to the EVAP system.

The stripped chassis:

test port is separate from the valve.
test port is fastened to the transmission fluid indicator tube.