2003 FORD MUSTANG Workshop Manual

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Page 2145 of 4378

FORD MUSTANG 2003 Workshop Manual DESCRIPTION AND OPERATION
Evaporative Emissions
Component Location
The evaporative emission system:
�zis equipped with an on- board refueling vapor recovery (ORVR) system.
SECTION 303-
13: Evapor

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FORD MUSTANG 2003 Workshop Manual �z
prevents hydrocarbon emissions from reaching the atmosphere.
�z stores fuel vapors in the evaporative emission (EVAP) canister that are generated during
vehicle operation or hot soak, or vehicle

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FORD MUSTANG 2003 Workshop Manual �z
is located in the right front inner fender well.
The fuel vapor control valve tube assembly:
�zconsists of the fuel vapor control valve, fuel vapor vent valve and an in- line fuel tank pressure

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FORD MUSTANG 2003 Workshop Manual DIAGNOSIS AND TESTING
Evaporative Emissions
Evaporative Emission System
SECTION 303-
13: Evaporative Emissions 2003 Mustang Workshop Manual Special Tool(s)
Evaporative Emission System
Leak Teste

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FORD MUSTANG 2003 Workshop Manual Principles of Operation
Evaporative Emission (EVAP) Canister Purge Valve
The EVAP canister purge valve is controlled by the powertrain control module (PCM). The EVAP
canister purge valve controls t

Principles of Operation
Evaporative Emission (EVAP) Canister Purge Valve
The EVAP canister purge valve is controlled by the powertrain control module (PCM). The EVAP
canister purge valve controls the flow of fuel vapors from the EVAP canister to the engine intake
manifold during various engine operating modes. The EVAP canister purge valve is normally closed.
Evaporative Emission (EVAP) Canister
Fuel vapors from the fuel tank are stored in the EVAP canister. When the engine is running, the vapors
are purged from the EVAP canister for combustion.
Canister Vent Solenoid
During the Evaporative Emission (EVAP) System Test Monitor, Evaporative Emissions Repair
Verification Drive Cycle, and the Evaporative Emission System Leak Test, the canister vent solenoid is
closed to allow a vacuum to be drawn on the fuel tank at a specific level. The canister vent solenoid is
normally open.
Fuel Tank Pressure (FTP) Sensor
The fuel tank pressure sensor is used to measure the fuel tank pressure during the Evaporative
Emissions Monitor Test. The fuel tank pressure sensor is mounted in the fuel vapor control valve tube
as it crosses over the fuel tank.
Fuel Vapor Control Valve
The fuel vapor control valve is normally between the EVAP canister and the fuel vapor vent valve. Its
function is to prevent the flow of liquid fuel into the EVAP canister or up to the canister purge valve
during refueling, and to prevent the collection of liquid fuel in the fuel vapor hoses by overfilling the fuel
tank.
Fuel Vapor Vent Valve (FVV) Assembly
The fuel vapor vent valve (FVV) 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 intricate part of the fuel filler pipe. It is intended to prevent liquid
fuel from re-entering the fuel filler pipe from the fuel tank on refueling or roll over conditions.
Fuel Filler Cap
The fuel filler cap is used to prevent fuel spill and to close the EVAP system to the atmosphere.
Evaporative Emission 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 Emission System Leak Test Klj . 2 ba
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FORD MUSTANG 2003 Workshop Manual To start the testing, conditions of stable purging and vehicle speed must be satisfied. During the first
stage, the canister vent solenoid is closed, while the EVAP canister purge valve remains open,

To start the testing, conditions of stable purging and vehicle speed must be satisfied. During the first
stage, the 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 EVAP 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.
On-
Board Refueling Vapor Recovery (ORVR) Evaporative Emission (EVAP) System
The basic elements forming the ORVR system are as follows:
zThe 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.
z A fuel vapor control valve controls the flow of vapors out of the fuel tank. The valve closes when
the liquid level reaches a height associated with fuel tank usable capacity. The valve
accomplishes the following:
„limits the total amount of fuel that can be dispensed into the fuel tank
„ prevents liquid gasoline from exiting the fuel tank when submerged (as well as when
tipped well beyond a horizontal plane as part of the vehicle rollover protection in road
accidents)
„ minimizes vapor flow resistance during anticipated refueling conditions
z 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.
z A check valve in the fuel filling system 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 by the engine.
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 Mechanical
z
Fuel filler cap
z EVAP test port
z EVAP canister or canister vent solenoid Klj . 3 ba
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FORD MUSTANG 2003 Workshop Manual 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 men

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:
zcheck that the program card is correctly installed.
z check the connections to the vehicle.
z 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:
z CKT914, CKT915 or CKT70 = ALL ECUS NO RESP/NOT EQUIP, refer to Section 418 - 00 .
z NO RESP/NOT EQUIP for PCM, refer to the Powertrain Control/Emissions Diagnosis (PC/ED)
manual.
z SYSTEM PASSED, retrieve and record the continuous diagnostic trouble codes (DTCs), erase
the continuous DTCs and carry out the PCM KOEO self- test.
6. If the DTCs retrieved are related to the concern, go to the PCM Diagnostic Trouble Code (DTC) Index to continue diagnostics.
7. If the concern remains after the inspection, determine the symptom. GO to Symptom Chart .
PCM Diagnostics Trouble Code (DTC) Index
Symptom Chart z
EVAP lines or hoses
z Vacuum lines or hoses DTC Description Source Action
P0442 Small leak detected in EVAP system
(As small as 1.02 mm [0.040 inch]) PCM Go To Pinpoint Test A .
P0455 Major leak or no flow detected PCM Go To Pinpoint Test B .
P0457 Check for missing or leaking fuel filter
cap PCM Go To Pinpoint Test A .
P1443 Very small or no purge flow detected PCM Go To Pinpoint Test B .
P1450 Excessive vacuum detected in the fuel
tank PCM Go To Pinpoint Test C .
— Any other PCM DTC PCM REFER to the Powertrain
Control/Emissions Diagnosis (PC/ED)
manual.
SYMPTOM CHART Condition
Possible Sources Action
z Hissing sound when
removing fuel cap z
Canister vent solenoid.
z Evaporative emissions
canister.
z Fuel vapor control valve z
Go To Pinpoint Test D . Klj . 4 ba
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FORD MUSTANG 2003 Workshop Manual Pinpoint Tests
NOTE:
Reinstall or install new evaporative emission hose clamps removed or damaged during testing
procedures.
PINPOINT TEST A: DTC P0442 SMALL LEAK IN EVAP SYSTEM tube assembly.
�

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