AutoZone 1963 Mercury Monterey 6.4L 2BL 8cyl | Repair Guides | Driveability & Emissions Controls | Emission Controls | Evaporative Emission Control System | AutoZone.com

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    GM Bonneville/Eighty Eight/LeSabre 1986-1999

    Evaporative Emission Control System

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    OPERATION



    See Figures 1, 2 and 3

    The Evaporative Emission Control (EVAP) System is designed to prevent fuel tank vapors from being emitted into the atmosphere. When the engine is not running, gasoline vapors from the tank are stored in a charcoal canister, mounted under the hood. The charcoal canister absorbs the gasoline vapors and stores them until certain engine conditions are met and the vapors can be purged and burned by the engine. In some vehicles with fuel injection, any liquid fuel entering the canister goes into a reservoir in the bottom of the canister to protect the integrity of the carbon element in the canister above. Three different methods are used to control the purge cycle of the charcoal canister.

    First, the charcoal canister purge cycle is controlled by throttle position without the use of a valve on the canister. A vacuum line connects the canister to a ported vacuum source on the throttle body. When the throttle is at any position above idle, fresh air is drawn into the bottom of the canister and the fuel vapors are carried into the throttle body at that port. The air/vapor flow volume is only what can be drawn through the vacuum port and is fairly constant.



    Click image to see an enlarged view

    Fig. Fig. 1: Evaporative emission control system schematic

    Second, the flow volume is modulated with throttle position through a vacuum valve. The ported vacuum from the throttle body is used to open a diaphragm valve on top of the canister. When the valve is open, air and vapors are drawn into the intake manifold, usually through the same manifold port as the PCV system. With this method, the purge valve cycle is slaved to the throttle opening; more throttle opening, more purge air flow.

    And third, the charcoal canister purge valve cycle is controlled by the ECM through a solenoid valve on the canister. When the solenoid is activated, full manifold vacuum is applied to the top of the purge valve diaphragm to open the valve all the way. A high volume of fresh air is drawn into the canister and the gasoline vapors are purged quickly. The ECM activates the solenoid valve when the following conditions are met:

    1. The engine is at normal operating temperature.
    2.  
    3. After the engine has been running a specified period of time.
    4.  
    5. Vehicle speed is above a predetermined speed.
    6.  
    7. Throttle opening is above a predetermined value.
    8.  

    A vent pipe allows fuel vapors to flow to the charcoal canister. On some vehicles, the tank is isolated from the charcoal canister by a tank pressure control valve, located either in the tank or in the vapor line near the canister. It is a combination roll-over, integral pressure and vacuum relief valve. When the vapor pressure in the tank exceeds 0.72 psi (5 kPa), the valve opens to allow vapors to vent to the canister. The valve also provides vacuum relief to protect against vacuum build-up in the fuel tank and roll-over spill protection.

    Click image to see an enlarged view

    Fig. Fig. 2: Typical EVAP canister and vacuum line connections

    Poor engine idle, stalling and poor driveability can be caused by an inoperative canister purge solenoid, a damaged canister or split, damaged or improperly connected hoses.



    Click image to see an enlarged view

    Fig. Fig. 3: There is a canister purge valve/solenoid on top of the EVAP canister

    The most common symptom of problems in this system is fuel odors coming from under the hood. If there is no liquid fuel leak, check for a cracked or damaged vapor canister, inoperative or always open canister control valve, disconnected, misrouted, kinked or damaged vapor pipe or canister hoses; or a damaged air cleaner or improperly seated air cleaner gasket.

    TESTING



    Charcoal Canister
    1. Visually check the canister for cracks or damage.
    2.  
    3. If fuel is leaking from the bottom of the canister, replace canister and check for proper hose routing.
    4.  
    5. Check the filter at the bottom of the canister. If dirty, replace the filter.
    6.  

    Tank Pressure Control Valve

    1. Using a hand-held vacuum pump, apply a vacuum of 11 in. Hg (51 kPa) through the control vacuum signal tube to the purge valve diaphragm. If the diaphragm does not hold vacuum for at least 16 seconds, the diaphragm is leaking. Replace the control valve.
    2.  
    3. With the vacuum still applied to the control vacuum tube, attach a short piece of hose to the valve's tank tube side and blow into the hose. Air should pass through the valve. If it does not, replace the control valve.
    4.  

    Canister Purge Control Valve

    1. Connect a clean length of hose to the fuel tank vapor line connection on the canister and attempt to blow through the purge control valve. It should be difficult or impossible to blow through the valve. If air passes easily, the valve is stuck open and should be replaced.
    2.  
    3. Connect a hand-held vacuum pump to the top vacuum line fitting of the purge control valve. Apply a vacuum of 11 in. Hg (51 kPa) to the purge valve diaphragm. If the diaphragm does not hold vacuum for at least 16 seconds the diaphragm is leaking. Replace the control valve. If it is impossible to blow through the valve, it is stuck closed and must be replaced.
    4.  
    5. On vehicles with a solenoid activated purge control valve, unplug the connector and use jumper wires to supply 2 volts to the solenoid connections on the valve. With the vacuum still applied to the control vacuum tube, the purge control valve should open and it should be easy to blow through. If not, replace the valve.
    6.  

    REMOVAL & INSTALLATION



    Charcoal Canister
    1987-95 VEHICLES

    See Figures 4, 5, 6, 7, 8 and 9

    1. Disconnect the negative battery cable.
    2.  
    3. For 1995 vehicles, perform the following:
      1. Remove the air cleaner box assembly.
      2.  
      3. Remove the windshield washer reservoir.
      4.  
      5. Remove the load level pump.

        Click image to see an enlarged view

        Fig. Fig. 4: EVAP canister electrical connector (1), purge solenoid (2) and vacuum hoses (3)

      6.  

    4.  
    5. If equipped, detach the electrical connector.
    6.  



    Click image to see an enlarged view

    Fig. Fig. 5: Unplug the canister purge solenoid electrical connector

    1. Tag and disconnect the hoses from the canister.
    2.  



    Click image to see an enlarged view

    Fig. Fig. 6: Disconnect the vacuum line(s) from the purge solenoid ...



    Click image to see an enlarged view

    Fig. Fig. 7: ... and from the nipple on the canister

    1. Unfasten the charcoal canister retaining nut or hold-down strap.
    2.  



    Click image to see an enlarged view

    Fig. Fig. 8: Unfasten the canister hold-down strap retaining bolt ...



    Click image to see an enlarged view

    Fig. Fig. 9: ... then lift the canister up and out of the vehicle

    1. Remove the canister from the vehicle.
    2.  

    To install:
    1. Position the charcoal canister in the vehicle. Install the canister retaining nut or hold-down strap, as applicable, and tighten to 25 inch lbs. (3 Nm).
    2.  
    3. Connect the hoses to the canister, as tagged during removal. Refer to the Vehicle Emission Control Information label, located in the engine compartment, to make sure you have the vacuum hoses properly routed.
    4.  
    5. If equipped, attach the electrical connector.
    6.  
    7. For 1995 vehicles, perform the following:
      1. Install the load level pump.
      2.  
      3. Install the windshield washer reservoir.
      4.  
      5. Install the air cleaner box assembly.
      6.  

    8.  
    9. Connect the negative battery cable.
    10.  

    1996-98 VEHICLES

    See Figure 10

    1. Disconnect the negative battery cable.
    2.  
    3. Remove the PCM from the vehicle, as outlined later in this section.
    4.  
    5. For 3.8L (VIN K) engines, remove the EVAP canister vent valve/solenoid.
    6.  
    7. Remove the PCM bracket attaching hardware, then remove the PCM bracket.
    8.  
    9. Remove the EVAP canister vent valve/solenoid bracket.
    10.  
    11. Tag and disconnect the purge, fuel vapor, and vent lines from the EVAP canister.
    12.  
    13. Remove the canister from the vehicle.
    14.  



    Click image to see an enlarged view

    Fig. Fig. 10: Evaporative canister mounting - 1996-98 vehicles

    To install:
    1. Install the EVAP canister in the vehicle.
    2.  
    3. Connect the EVAP vent hose, then tighten the hose clamp securely.
    4.  
    5. Attach the purge and vapor lines to the canister, as tagged during removal.
    6.  
    7. Install the valve vent bracket. Tighten the retainers to 12 inch lbs. (2 Nm).
    8.  
    9. Install the PCM bracket.
    10.  
    11. Install the EVAP canister vent valve.
    12.  
    13. Install the 2 PCM bracket bolts, and 2 bracket retainers.
    14.  
    15. Install the PCM, as outlined later in this section.
    16.  
    17. Connect the negative battery cable.
    18.  

    Canister Purge Solenoid/Valve

    1987-95 VEHICLES
    1. Disconnect the negative battery cable.
    2.  

    On some 1994-95 vehicles, it is necessary to remove the canister for access to the purge solenoid/valve.

    1. If necessary, remove the EVAP canister.
    2.  
    3. Detach the electrical connector and hoses from the solenoid.
    4.  
    5. Remove the canister purge solenoid/valve from the canister.
    6.  

    To install:
    1. Install the canister purge solenoid/valve on the canister.
    2.  
    3. Attach the hoses and electrical connector to the solenoid/valve.
    4.  
    5. If removed, install the EVAP canister.
    6.  
    7. Connect the negative battery cable.
    8.  

    1996-98 VEHICLES

    See Figure 11

    1. Disconnect the negative battery cable.
    2.  
    3. Detach the electrical connector and hoses from the EVAP purge solenoid.
    4.  
    5. Bend the tab on the solenoid mounting bracket to remove the EVAP purge solenoid.
    6.  



    Click image to see an enlarged view

    Fig. Fig. 11: Location of the EVAP purge solenoid (1) and vacuum switch (2) mounting - 1996-97 vehicles



    Click image to see an enlarged view

    Fig. Fig. 12: After detaching the electrical connector and vacuum line, remove the purge solenoid - 1998 3.8L (VIN K) engine



    Click image to see an enlarged view

    Fig. Fig. 13: Exploded view of the solenoid and related components - 1998 3.8L (VIN 1) engine

    To install:
    1. Bend the tab on the solenoid mounting bracket to install the solenoid.
    2.  
    3. Install the solenoid.
    4.  
    5. Attach the hoses and electrical connector to the solenoid.
    6.  
    7. Connect the negative battery cable.
    8.  

    Tank Pressure Control Valve

    1. Disconnect the hoses from the control valve.
    2.  
    3. Remove the mounting hardware.
    4.  
    5. Remove the control valve from the vehicle.
    6.  
    7. Installation is the reverse of the removal procedure. Tighten the retainers to 25 inch lbs. (3 Nm).
    8.  

    Refer to the Vehicle Emission Control Information label, located in the engine compartment, for proper routing of the vacuum hoses.

    EVAP Vacuum Switch
    1996-97 VEHICLES
    1. Disconnect the negative battery cable.
    2.  
    3. Detach the electrical connector and the vacuum hoses from the EVAP vacuum switch.
    4.  
    5. Bend the tab on the vacuum switch mounting bracket to remove the switch.
    6.  

    To install:
    1. Attach the EVAP vacuum switch to the mounting bracket.
    2.  
    3. Attach the hoses and electrical connector to the vacuum switch.
    4.  
    5. Connect the negative battery cable.
    6.  

    EVAP Vent Valve

    See Figure 14

    1. Disconnect the negative battery cable.
    2.  
    3. Remove the PCM, as outlined later in this section.
    4.  
    5. Detach the EVAP canister vent valve from the vent valve bracket.
    6.  
    7. Unplug the canister vent valve electrical connector.
    8.  
    9. Loosen the vent hose clamp and remove the vent hose from the EVAP vent valve.
    10.  
    11. Remove the EVAP canister vent valve from the vehicle.
    12.  



    Click image to see an enlarged view

    Fig. Fig. 14: Exploded view of the EVAP vent valve mounting

    To install:
    1. Connect the vent hose to the EVAP canister vent valve and tighten the hose clamp.
    2.  
    3. Attach the vent valve electrical connector.
    4.  
    5. Install the EVAP canister vent valve to the valve bracket.
    6.  
    7. Install the PCM, as outlined later in this section.
    8.  
    9. Connect the negative battery cable.
    10.  

    EVAP Pipes

    Do not try to repair the EVAP pipes or the connecting hoses. Replace any damaged hoses or pipes. If the nylon EVAP pipe becomes kinked and cannot be straightened, it must be replaced.

    1996-97 VEHICLES

    See Figure 15

    1. Raise and safely support the vehicle.
    2.  
    3. Remove the hardware retaining the EVAP pipes.
    4.  
    5. Inspect the location of the attaching hardware for installation.
    6.  
    7. Remove the EVAP pipe.
    8.  
    9. Inspect the pipe for bends, kinks, and cracks.
    10.  



    Click image to see an enlarged view

    Fig. Fig. 15: Raise the vehicle to access the EVAP lines under the vehicle

    To install:

    The EVAP pipe must be properly secured in order to prevent chafing of the EVAP pipe. Always re-attach the fuel lines and fuel filter with all original type fasteners and hardware.

    1. Install the EVAP pipe, and secure with the retaining hardware.
    2.  
    3. Carefully lower the vehicle.
    4.  

    1998 3.8L ENGINE - ENGINE PIPES
    1. Remove the fuel injector sight shield.
    2.  
    3. Unfasten any necessary hardware retaining the EVAP pipe.
    4.  
    5. Inspect the location of the attaching hardware for installation.
    6.  
    7. Remove the EVAP pipe/hose. Inspect the pipe/hose for bends, kinks and cracks.
    8.  
    9. Replace the pipes/hoses as required.
    10.  
    11. Installation is the reverse of the removal procedure. Make sure to properly secure the pipe in order to prevent chafing.
    12.  

    1998 3.8L ENGINE - CANISTER-TO-FUEL TANK PIPES

    See Figure 16

    1. Properly relieve the fuel system pressure, as outlined in Fuel System of this repair guide.
    2.  
    3. If not done already, disconnect the negative battery cable.
    4.  
    5. Raise and safely support the vehicle.
    6.  
    7. Remove the fuel tank, as outlined in Fuel System of this repair guide.
    8.  
    9. Unfasten the hardware retaining the EVAP pipes, noting the location for installation.
    10.  
    11. Remove the in-line fuel filter.
    12.  
    13. Partially lower the vehicle for access to the engine compartment.
    14.  
    15. Remove the PCM, as outlined later in this section.
    16.  
    17. Remove the PCM base holder.
    18.  



    Click image to see an enlarged view

    Fig. Fig. 16: Remove the PCM base holder

    1. Disconnect the EVAP pipes from the canister.
    2.  
    3. Remove the EVAP pipes from the fuel tank
    4.  
    5. Remove the EVAP pipes from the vehicle.
    6.  

    To install:

    Make sure to route the replacement EVAP pipe in exactly the same orientation as the original.

    1. Install the fuel tank.
    2.  

    Secure the EVAP pipe in order to prevent chafing the pipe.

    1. Install the EVAP pipes to the chassis and secure with the pipe retainers. Tighten to 71 inch lbs. (8 Nm).
    2.  
    3. Install the in-line fuel filter.
    4.  
    5. Carefully lower the vehicle.
    6.  
    7. Connect the EVAP pipes to the canister. Route the main body harness outboard along the inner fender and wheelhouse to allow for the installation of the PCM base.
    8.  
    9. Install the PCM base holder and the PCM.
    10.  
    11. Add fuel and install the fuel tank filler cap.
    12.  
    13. Connect the negative battery cable. Turn the ignition ON for 2 seconds, OFF for 10 seconds, then ON again and check for fuel leaks.
    14.  

     
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