Chrysler Caravan/Voyager/Town and Country 1996-1999

Evaporative Emission Controls

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OPERATION



See Figure 1



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Fig. Fig. 1: Evaporative system monitor schematic-1996-97 models shown, 1998-99 similar

The evaporation control system prevents the emission of fuel tank vapors into the atmosphere. When fuel evaporates in the fuel tank, the vapors pass through vent hoses or tubes to a charcoal filled evaporative canister. This canister holds the vapors temporarily. The Powertrain Control Module (PCM) allows intake manifold vacuum to draw vapors into the combustion chambers during certain operating conditions.

The evaporative system utilizes specially manufactured hoses. If they are in need of replacement, use only fuel resistant hoses.

All engines utilize a duty cycle purge system. The PCM controls vapor flow by operating the duty cycle EVAP purge solenoid. The evaporation control system is made up of the following components:

Crankcase Vent Filter

All engines use filtered air to vent the crankcase. The filtered air is drawn through the resonator assembly located between the air cleaner and the throttle body.

Pressure Relief/Rollover Valve

All Chrysler minivans are equipped with rollover valve(s). The rollover valve is a safety device which prevents fuel flow through the fuel tank vent valve hoses, should the vehicle roll over in an accident. The rollover valve is located on top of the fuel tank. In order to access the rollover valve, the fuel tank must be removed; however, the valve is not a serviceable component.

EVAP Canister

See Figure 2



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Fig. Fig. 2: Evaporative canister and vacuum hose identifications

All vehicles use a sealed, maintenance-free evaporative (EVAP) canister. Fuel tank pressure vents into the canister. The canister temporarily holds the fuel vapors until intake manifold vacuum draws them into the combustion chamber. The canister proportional purge solenoid allows the canister to be purged at predetermined intervals and engine conditions.

On all Chrysler minivans, the canister mounts to the vehicle frame underneath the driver's seat. There is no scheduled maintenance interval for the charcoal canister.

Duty Cycle EVAP Canister Purge Solenoid

See Figure 3



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Fig. Fig. 3: Duty Cycle EVAP Purge solenoid

All 1996-97 Chrysler minivans come equipped with a Duty Cycle Evap Canister Purge solenoid. The Duty Cycle EVAP Canister Purge solenoid regulates the rate of vapor flow from the EVAP canister to the throttle body. The PCM operates the solenoid. During the cold start warm-up period and the hot start time delay, the PCM does not energize the solenoid. When de-energized, no vapors are purged. The PCM de-energizes the solenoid during open loop operation.

The engine enters closed loop operation after it reaches a specific temperature and the time delay ends. During closed loop operation, the PCM energizes and de-energizes the solenoid about 5-10 times per second, depending upon operating conditions. The PCM varies the vapor flow rate by changing the solenoid pulse width. Pulse width is the amount of time the solenoid energizes. The PCM adjusts solenoid pulse width based on engine operating conditions.

The solenoid is mounted on a bracket, located on the right engine mount. The solenoid will not operate properly unless it is installed with the electrical connector at the top.

Proportional Purge Solenoid

See Figure 4



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Fig. Fig. 4: Proportional Purge solenoid

All 1998-99 Chrysler minivans come equipped with a Proportional Purge solenoid. The solenoid regulates the rate of vapor flow from the EVAP canister to the throttle body. The PCM operates the solenoid. During the cold start warm-up period and the hot start time delay, the PCM does not energize the solenoid. When de-energized, no vapors are purged.

The solenoid operates at a frequency of 200 Hz and is controlled by an engine controller circuit that senses the current being applied to the solenoid, then adjusts that same current to achieve the desired purge flow. The proportional purge solenoid controls the purge rate of the fuel vapors from the EVAP canister and fuel tank to the engine intake manifold.

Pressure Vacuum Filler Cap

See Figure 5



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Fig. Fig. 5: Pressure vacuum filler cap

A pressure vacuum relief cap is used to seal the fuel tank. Tightening the cap on the fuel filler tube creates a seal between them. The relief valves in the cap are a safety feature which prevent possible excessive pressure or vacuum in the fuel tank. Excessive fuel tank pressure could be caused by a malfunction in the system or damage to the vent lines.

When the cap is removed, the seal is broken and fuel tank pressure is relieved. If the filler cap ever needs to be replaced, make sure to get the correct part.

Leak Detection Pump

See Figure 6



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Fig. Fig. 6: Leak detection pump

All Chrysler minivans utilize a leak detection pump, which is a device used to find leaks in the evaporative emission system. The pump has a 3-port solenoid, a pump that contains a switch, a spring loaded canister vent valve seal, 2 check valves and a spring/diaphragm.

component testing

Evaporative System Check

See Figures 1, 2 and 7

  1. Before beginning the check, inspect all connectors for a clean, tight fit.
  2.  
  3. Start the engine and allow it to reach normal operating temperatures.
  4.  
  5. Inspect the throttle body-to-evaporative emission solenoid vacuum line. Check for vacuum leaks or restrictions. If the vacuum line is damaged, replace or repair as necessary. If the line is OK, proceed with the test.
  6.  



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Fig. Fig. 7: Vacuum line identifications to the EVAP solenoid-1996-97 models shown

  1. Check the vacuum line running from the evaporative solenoid to the canister for damage or restriction. If the vacuum line is damaged, replace or repair as necessary. If the line is OK, proceed with the test.
  2.  

Allow the engine to idle for 2 minutes after reaching normal operating temperature.

  1. Disconnect the canister-to-solenoid vacuum line from the solenoid. Is the evaporative solenoid allowing vacuum to cycle through intermittently at a steady rate- If not, replace the evaporative solenoid. If so, proceed with the test.
  2.  

During the next steps, do NOT use more than 5 psi of air pressure.

  1. Turn the ignition key to the OFF position. Attempt to blow air through the vacuum line that goes to the canister. Do the canister and vacuum line allow air to pass- If so, the purge solenoid and hoses are OK. If not, proceed with the test.
  2.  
  3. Disconnect the solenoid-to-canister vacuum line from the canister. Try to blow air through the vacuum line that goes to the canister. Does the line let air pass- If so, replace the evaporative canister. If not, repair or replace the vacuum line, as necessary.
  4.  

REMOVAL & INSTALLATION



Leak Detection Pump (LDP)

See Figures 6 and 8<