Fuel vapors from the fuel tank are stored in the EVAP canisters. When the engine is running, the vapors are purged from the EVAP canisters for combustion.
Canister Vent Solenoid
During the Evaporative Emission Running Loss System Monitor Test, Evaporative Emissions Repair Verification Drive Cycle, and the Evaporative Emission System
Leak Test, the canister vent solenoid is closed to allow either a vacuum to be drawn on the fuel tank or to hold a specified pressure in the system. The canister vent
solenoid is normally open.
Fuel Tank Pressure (FTP) Sensor
The fuel tank pressure (FTP) sensor is used to measure the fuel tank pressure during the Evaporative Emissions Monitor Test. It is also used to control excessive fuel
tank pressures by forcing the EVAP system to purge. The fuel tank pressure sensor is mounted in the main vapor line.
Fuel Vapor Vent (FVV) Valve Assembly
The fuel vapor vent (FVV) valve assembly is mounted on the top of the fuel tank. It is used to control the flow of fuel vapors entering the EVAP system. The head portion
of the assembly prevents the fuel tank from overfilling during refueling. The assembly also has a spring float, which prevents liquid fuel from entering the vapor delivery
system under severe handling or vehicle rollover conditions. In the upright position, the open bottom of the float will lift and shut off the orifice. Under severe handling
conditions, the spring will push the float closed when angles allow liquid fuel to reach the orifice. In a rollover condition, the weight of the open bottom float and spring
pressure will close the orifice.
Fuel Filler Pipe Check Valve
The fuel filler pipe check valve is an integral part of the fuel tank or the fuel filler pipe. It is intended to prevent liquid fuel from re-entering the fuel filler pipe from the fuel
tank after refueling.
Fuel Filler Cap
The fuel filler cap is used to prevent fuel spill and to close the EVAP system to the atmosphere.
Fill Limit Vent Valve (FLVV)
The fill limit vent valve is mounted on top of the fuel tank. It has a main orifice which allows fuel vapor to route to the carbon canisters during refueling. This orifice is
controlled by a float, when the tank is full the flow of vapor is stopped and prevents the tank from overfilling.
Evaporative Emission (EVAP) System Monitor
When a fault occurs, the EVAP system monitor is reset to NO and a diagnostic trouble code (DTC) is set in the PCM memory. After the DTC is repaired, the vehicle
drive cycle must be completed to reset the monitor in preparation for inspection and maintenance testing.
EVAP Running Loss System Leak Test
To start the testing, conditions of stable purging and vehicle speed must be satisfied. During the first stage, the EVAP canister vent solenoid is closed, while the EVAP
canister purge valve remains open, applying and building vacuum in the system as indicated by the FTP sensor. This phase checks for major leaks in the EVAP system.
In the second stage, the EVAP canister purge valve closes and the system looks for minimal decay rate in the vacuum, indicating the absence of any small EVAP
system leaks.
The last stage is entered only if stage two of the leak test has failed and checks whether the failed test was due to excess vapor generation. It monitors fuel vapor
generation rate. Initially, the canister vent solenoid is opened to equalize EVAP system pressure to atmosphere. Then the canister vent solenoid is closed, allowing
pressure to build if vapor generation is present in sufficient quantity. If the rate of generation is found to be too high, the EVAP running loss system leak test is aborted.
If not, then a small leak is diagnosed.
Inspection and Verification
1. Verify the customer concern is with the evaporative emission (EVAP) system.
2. Visually inspect for the following obvious signs of mechanical damage.
Visual Inspection Chart
3. If the concern remains after the inspection, connect the scan tool to the data link connector (DLC) located beneath the instrument panel and select the vehicle to
be tested from the scan tool menu. If the scan tool does not communicate with the vehicle:
check that the program card is correctly installed.
check the connections to the vehicle.
check the ignition switch position.
4. If the scan tool still does not communicate with the vehicle, refer to the scan tool manual.
5. Carry out the DATA LINK DIAGNOSTICS test. If the scan tool responds with:
CKT914, CKT915 or CKT70 = ALL ECUS NO RESP/NOT EQUIP, refer to
Section 418-00
.
NO RESP/NOT EQUIP for PCM, refer to the Powertrain Control/Emissions Diagnosis (PC/ED) manual.
Mechanical
Fuel filler cap
EVAP test port
EVAP canisters or vent solenoid
EVAP canister lines or hoses
Vacuum lines or hoses
Page 2 of 8
2004 Freestar/Monterey Workshop Manual
10/9/2010
http://www.fordtechservice.dealerconnection.com/pubs/content/~WS4W/~MUS~LEN/20/...
