Continental 2000-2002

Evaporative Emission Control (EEC) Systems

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Gasoline fuel is a major source of pollution, before and after it is burned in the automobile engine. From the time the fuel is refined, stored, pumped and transported, again stored until it is pumped into the fuel tank of the vehicle, the gasoline gives off unburned hydrocarbons (HC) into the atmosphere. Through the redesign of storage areas and venting systems, the pollution factor was diminished, but not eliminated, from the refinery standpoint. However, the automobile remained the primary source of vaporized, unburned hydrocarbon (HC) emissions.

Fuel pumped from an underground storage tank is cool but when exposed to a warmer ambient temperature, will expand. Before controls were mandated, an owner might fill the fuel tank with fuel from an underground storage tank and park the vehicle for some time in warm area, such as a parking lot. As the fuel warms, it expands and if no provisions were provided for the expansion, the fuel would spill out of the filler neck and onto the ground, causing hydrocarbon (HC) pollution and creating a severe fire hazard. To correct this condition, the vehicle manufacturers added overflow plumbing and/or gasoline tanks with built in expansion areas or domes.

However, this did not control the fuel vapor emission from the fuel tank. It was determined that most of the fuel evaporation occurred when the vehicle was stationary and the engine not operating. Most vehicles carry 5-25 gallons (19-95 liters) of gasoline. Should a large concentration of vehicles be parked in one area, such as a large parking lot, excessive fuel vapor emissions would take place, increasing as the temperature increases.

To prevent the vapor emission from escaping into the atmosphere, the fuel systems were designed to trap the vapors while the vehicle is stationary, by sealing the system from the atmosphere. A storage system is used to collect and hold the fuel vapors from the carburetor (if equipped) and the fuel tank when the engine is not operating. When the engine is started, the storage system is then purged of the fuel vapors, which are drawn into the engine and burned with the air/fuel mixture.

Operation



The evaporative emission control system prevents the escape of fuel vapors to the atmosphere under hot soak and engine off conditions by storing the vapors in a carbon canister. Then, with the engine warm and running, the system controls the purging of stored vapors from the canister to the engine, where they are efficiently burned.

Evaporative emission control components consist of the carbon canister, purge valve(s), vapor valve, rollover vent valve, check valve and the necessary lines. All vehicles may not share all components.

Carbon Canister

The carbon canister contains vapor absorbent material to facilitate the storage of fuel vapors. Fuel vapors flow from the fuel tank to the canister, where they are stored until purged to the engine for burning.



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Fig. Cross-section of a carbon canister

Fuel Tank Vapor Orifice And Roll Over Valve Assembly

Fuel vapor in the fuel tank is vented to the carbon canister through the vapor valve assembly. The valve is mounted in a rubber grommet at a central location in the upper surface of the fuel tank. A vapor space between the fuel level and the tank upper surface is combined with a small orifice and float shut-off valve in the vapor valve assembly to prevent liquid fuel from passing to the carbon canister. The vapor space also allows for thermal expansion of the fuel. The vapor valve incorporates the rollover valve. In the event of a vehicle rollover, the valve blocks the vapor line automatically to prevent fuel leakage.



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Fig. Fuel tank vapor orifice and roll over valve assembly

The check valve is located in the fuel filler cap or on the underside of the vehicle. Its function is to protect the fuel tank from heat build-up rupture and cool-down collapse by allowing air to pass in or out of the tank to equalize pressure. On cool-down, air enters either at the carbon canister vent or at the check valve.

Obd-II EVAP System Monitor

Some of the models covered in this manual have added system components due to the EVAP system monitor incorporated in the OBD-II engine control system. A pressure sensor is mounted on the fuel tank which measures pressure inside the tank, and a purge flow sensor measures the flow of the gases from the canister into the engine. The purge valve is now called the Vapor Management Valve (VMV). It performs the same functions as the purge valve, however it looks slightly different. A canister vent solenoid is mounted on the canister, taking the place of the vent cap, providing a source of fresh air to the canister.

The PCM can store trouble codes for EVAP system performance, a list of the codes is provided later in this section. Normal testing procedure can be used, see EVAP System Component Testing in this Section.

Pressure Vacuum Filler Cap

The fuel cap contains an integral pressure and vacuum relief valve. The vacuum valve acts to allow air into the fuel tank to replace the fuel as it is used, while preventing vapors from escaping the tank through the atmosphere. The vacuum relief valve opens after a vacuum of -0.5 psi. The pressure valve acts as a backup pressure relief valve in the event the normal venting system is overcome by excessive generation of internal pressure or restriction of the normal venting system. The pressure relief range is 1.6-2.1 psi. Fill cap damage or contamination that stops the pressure vacuum valve from working may result in deformation of the fuel tank.

Purge Control Valve

The purge valves control the flow of fuel vapor from the carbon canister to the engine. Purge valves are either vacuum or electrically controlled. When electrically controlled, a purge valve is known as a purge solenoid. A vehicle may be equipped with a vacuum purge valve or purge solenoid or a combination of the two. Purging occurs when the engine is at operating temperature and off idle.



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Fig. Purge control valve

Purge Solenoid Valve

The purge solenoid valve is in-line with the carbon canister and controls the flow of fuel vapors out of the canister. It is normally closed. When the engine is shut off, the vapors from the fuel tank flow into the canister. After the engine is started, the solenoid is engaged and opens, purging the vapors into the engine. With the valve open, vapors from the fuel tank are routed directly into the engine.



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Fig. Purge solenoid valve

Removal & Installation



Evaporative Emission Canister
  1. Disconnect the negative battery cable.
  2.  
  3. Label and disconnect the vapor hoses from the carbon canister.
  4.  
  5. Remove the canister attaching screws and remove the canister.
  6.  
  7. Installation is the reverse of the removal procedure.
  8.  

Fuel Tank Vapor Orifice & Rollover Valve Assembly
  1. Disconnect the negative battery cable.
  2.  
  3. Remove the fuel tank as described in Section 5.
  4.  
  5. Remove the vapor orifice and roll over valve assembly from the fuel tank.
  6.  
  7. Installation is the reverse of the removal procedure.
  8.  

Purge Control Solenoid Valve
  1. Disconnect the negative battery cable.
  2.  
  3. Label and disconnect the hoses from the purge control valve.
  4.  
  5. Remove the purge control valve.
  6.  
  7. Installation is the reverse of the removal procedure.
  8.  

  1. Disconnect the negative battery cable.
  2.  
  3. Label and disconnect the hoses from the purge solenoid valve.
  4.  
  5. Disconnect the electrical connector from the valve.
  6.  
  7. Remove the purge solenoid valve.
  8.  
  9. Installation is the reverse of the removal procedure.
  10.  

Service



The evaporative canister requires no periodic servicing. However, a careful inspection of the canister and hoses should be made frequently. Replace damaged components as required.



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Fig. Evaporative canister location-5.0L engine equipped vehicles

Testing



  1. Visually inspect the components of the evaporative emission system. Check for the following, as applicable:

    Discharged battery
     
    Damaged connectors
     
    Damaged insulation
     
    Malfunctioning PCM
     
    Damaged air flow meter or speed sensor
     
    Inoperative solenoids
     
    Fuel odor or leakage
     
    Damaged vacuum or fuel vapor lines
     
    Loose or poor line connections
     
    Poor driveability during engine warm-up
     

  2.  
  3. Check the wiring and connectors for the solenoids, vane air flow meter, speed sensor and PCM, as applicable, for looseness, corrosion, damage or other problems. This must be done with the engine fully warmed up so as to activate the purging controls.
  4.  
  5. Check the fuel tank, fuel vapor lines, vacuum lines and connections for looseness, pinching, leakage, damage or other obvious cause for malfunction.
  6.  
  7. If fuel line, vacuum line or orifice blockage is suspected as the obvious cause of an observed malfunction, correct the cause before proceeding further.
  8.  
  9. If applicable, check the wiring and connectors to the purge solenoid for looseness, corrosion, damage or other problems.
  10.  

 
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