Chrysler Full-Size Vans 1989-1998 Repair Guide

Evaporative Emission Controls

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OPERATION



See Figures 1, 2, 3 and 4

Changes in atmospheric temperature cause fuel tanks to breathe, that is, the air within the tank expands and contracts with outside temperature changes. If an unsealed system was used, when the temperature rises, air would escape through the tank vent tube or the vent in the tank cap. The air which escapes contains gasoline vapors.

The Evaporative Emission Control System provides a sealed fuel system with the capability to store and condense fuel vapors. When the fuel evaporates in the fuel tank, the vapor passes through vent hoses or tubes to a carbon filled evaporative canister. When the engine is operating the vapors are drawn into the intake manifold.

The vapors are drawn into the engine at idle as well as at operating speeds. This system is called a Bi-level Purge System where there is a dual source of vacuum to remove fuel vapor from the canister. The source of vacuum at idle is a tee in the PCV system.

A sealed, maintenance free evaporative canister is used. The canister is mounted under the vehicle on either side behind the wheel well. The canister is filled with granules of an activated carbon mixture. Fuel vapors entering the canister are absorbed by the charcoal granules.

Fuel tank pressure vents fuel vapors into the canister. They are held in the canister until they can be drawn into the intake manifold. The canister purge solenoid allows the canister to be purged at a predetermined time and engine operating conditions.

Vacuum for the canister is controlled by the canister purge solenoid. The solenoid is operated by the engine controller. The controller regulates the solenoid by switching the ground circuit on and off based on engine operating conditions. When energized, the solenoid prevents vacuum from reaching the canister. When not energized the solenoid allows vacuum to flow through to the canister.

During warm up and for a specified time after hot starts, the engine controller energizes (grounds) the solenoid preventing vacuum from reaching the canister. When the engine temperature reaches the operating level of about 120°F (49°C), the engine controller removes the ground from the solenoid allowing vacuum to flow through the canister and purges vapors through the throttle body. During certain idle conditions, the purge solenoid may be grounded to control fuel mix calibrations.

The fuel tank is sealed with a pressure-vacuum relief filler cap. The relief valves in the cap are a safety feature, preventing excessive pressure or vacuum in the fuel tank. If the cap is malfunctioning, and needs to be replaced, ensure that the replacement is the identical cap to ensure correct system operation.

During warm up and for a specified time after hot starts, the engine controller energizes (grounds) the solenoid preventing vacuum from reaching the canister. When the engine temperature reaches the operating level of about 120°F (49°C), the engine controller removes the ground from the solenoid allowing vacuum to flow through the canister and purges vapors through the throttle body. During certain idle conditions, the purge solenoid may be grounded to control fuel mix calibrations.

1996-98 vehicles have added system components due to the EVAP system monitor incorporated in the OBD-II engine control system used on these years. Two, instead of one, EVAP canisters are used and they are mounted on the drivers side of the vehicle instead of the passenger side. The canister purge solenoid is located on the bracket with the canisters. A Leak Detection Pump (LDP) is used to actually monitor the EVAP system for leaks. It is located on the driver's side inner fender wheelhouse. A test port for pressurizing the EVAP system is included and located below the brake booster on a tube that comes off the LDP. The test port is used to pressurize the system with a special gas and serious precautions must be taken to avoid damage to the EVAP system and the fuel tank. This is a procedure best suited to a professional shop, due to the precautions and the equipment needed to test this system. The ECM can store trouble codes for EVAP system performance, a list of the codes is provided later in this information. Normal testing procedure can be used for any component listed in EVAP testing in this guide.



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Fig. Fig. 1: Dual EVAP canister location-1996-98 vehicles



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Fig. Fig. 2: LDP equipped EVAP system component locations



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Fig. Fig. 3: EVAP system test port location on 1996-98 vehicles



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Fig. Fig. 4: A typical fuel tank filler tube cap

COMPONENT TESTING



To relieve fuel tank pressure, the filler cap must be removed before disconnecting any fuel system component.

Canister Purge Solenoid

See Figures 5 and 6

  1. Remove the engine cover.
  2.  
  3. With the ignition off, unplug the connector on the EVAP solenoid.
  4.  
  5. Turn ignition on, measure the voltage at the ignition switch output line, voltage should be 10.0v or more. If voltage is not 10.0v or more, repair circuit from ignition switch to EVAP solenoid.
  6.  
  7. Disconnect the negative battery cable.
  8.  
  9. Disconnect the ECM harness from the ECM.
  10.  
  11. Check the resistance of the EVAP solenoid control circuit between the ECM harness connector and the EVAP solenoid connector. Resistance should be less than 5.0 ohms; if not, repair the opening in the circuit.
  12.  
  13. Install the engine cover.
  14.  
  15. Connect the negative battery cable.
  16.  



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Fig. Fig. 5: EVAP solenoid circuits and schematic



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Fig. Fig. 6: EVAP solenoid electrical connector

REMOVAL & INSTALLATION



To relieve fuel tank pressure, the filler cap must be removed before disconnecting any fuel system component.

Evaporative (Carbon) Canister

See Figures 7, 8, 9, 10, 11 and 12

  1. Disconnect the negative battery cable.
  2.  
  3. Raise and support the vehicle.
  4.  
  5. Label and disconnect the hoses on the top of the canister.
  6.  
  7. Remove the bolt on the canister retaining strap.
  8.  
  9. Remove the two-piece strap and canister together.
  10.  

To install:
  1. Install the two-piece strap and canister in the mounting bracket.
  2.  
  3. Install and tighten the retaining strap bolt to 95 inch lbs. (10 Nm).
  4.  
  5. Install the hoses in their proper locations.
  6.  
  7. Lower the vehicle.
  8.  
  9. Connect the negative battery cable.
  10.  



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Fig. Fig. 7: EVAP canister and hoses



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Fig. Fig. 8: Location of the EVAP canister on pre-1996 vehicles



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Fig. Fig. 9: Exploded view of EVAP canister mounting on pre-1996 vehicles



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Fig. Fig. 10: Remove the bolt on the strap retaining the canister



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Fig. Fig. 11: Mark the lines connected to the EVAP canister before removal to ease installation



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Fig. Fig. 12: LDP mounting position on 1996-98 vehicles

Canister Purge Solenoid

See Figures 13 and 14

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the engine cover.
  4.  
  5. Disconnect the solenoid wiring harness.
  6.  
  7. Disconnect the vacuum harness.
  8.  
  9. The rest of the procedure is different for some model years. The differences are as follows:
    1. On 1989-92 TBI vehicles, remove the solenoid mounting pack as an assembly. Depress the tab on top of the purge solenoid and slide the solenoid downward to release it from the bracket.
    2.  
    3. On 1993-95 MFI vehicles, remove the solenoid and support bracket as an assembly.
    4.  
    5. On 1996-98 vehicles, remove the solenoid from the support bracket.
    6.  

  10.  

To install:


The procedures for the different model years are as follows:
  1. On 1989-92 TBI vehicles, install a new solenoid onto the solenoid pack bracket, and snap the retaining tab into place. Mount the solenoid pack onto the vehicle and tighten the retaining bolts.
  2.  
  3. On 1993-95 MFI vehicles, install the bracket and solenoid assembly onto the vehicle and tighten the retaining bolts.
  4.  
  5. On 1996-98 vehicles, install the solenoid onto the support bracket.
  6.  

 



Connect the vacuum harness.
 
Connect the wiring harness.
 
Install the engine cover.
 
Connect the negative battery cable.
 



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Fig. Fig. 13: Canister purge solenoid location-early vehicles



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Fig. Fig. 14: Canister purge solenoid location-later vehicles

 
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