GM Cavalier/Sunfire 1995-2000 Repair Guide

Evaporative Emission Control System

Print

OPERATION



See Figures 1, 2 and 3



Click image to see an enlarged view

Fig. Fig. 1: EVAP system schematic-1995 models



Click image to see an enlarged view

Fig. Fig. 2: EVAP system schematic-1996-00 models



Click image to see an enlarged view

Fig. Fig. 3: Cross-sectional view of an EVAP canister-1995 vehicle shown

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 the pressure control valve, through vent hoses or tubes to a carbon filled evaporative canister. When the engine is operating, and at normal operating temperature, the vapors are drawn into the intake manifold and burned during combustion..

A sealed, maintenance free evaporative canister is used. The canister is filled with granules of an activated carbon mixture. Fuel vapors entering the canister are absorbed by the charcoal granules. A vent cap is located on the top of the canister to provide fresh air to the canister when it is being purged. The vent cap opens to provide fresh air into the canister, which circulates through the charcoal, releasing trapped vapors and carrying them to the engine to be burned.

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 valve allows the canister to be purged at a pre-determined time and engine operating conditions.

Vacuum to the canister is controlled by the canister purge valve. The valve is operated by the PCM. The PCM regulates the valve by switching the ground circuit on and off based on engine operating conditions. When energized, the valve prevents vacuum from reaching the canister. When not energized the valve allows vacuum to purge the vapors from the canister.

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

The fuel tank is sealed with a pressure-vacuum relief filler cap. The relief valve in the cap is 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.

OBD-II EVAP System Monitor

See Figure 4



Click image to see an enlarged view

Fig. Fig. 4: 1996 and later vehicles with OBD-II are outfitted with a test port to connect a pressure tester to measure leakage in the EVAP system

1996-00 models 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 vent valve for the canister is now controlled by the PCM. 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.

As part of the OBD-II diagnostic system, a test port is installed in the purge line connecting the purge solenoid to the canister. This test port is used to connect a special tester that pressurizes the EVAP system and measure the leakage rate. This tool is very expensive and requires training to operate or you could do damage to the vehicle, however, many professional shops have this device. If you suspect a leak in your EVAP system, you may want to consult a professional shop about performing this test on your car.

TESTING



Evaporative Emissions Canister

Generally, the only testing done to the canister is a visual inspection. Look the canister over and replace it with a new one if there is any evidence of cracks or other damage.

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 purge control 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 15 in. Hg (51 kPa) to the purge valve diaphragm. If the diaphragm does not hold vacuum for at least 20 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 12 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.  

Tank Pressure Control Valve

See Figure 5



Click image to see an enlarged view

Fig. Fig. 5: Cross-sectional view of the fuel tank pressure control valve

  1. Using a hand-held vacuum pump, apply a vacuum of 15 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 20 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.  

Tank Pressure Sensor (199600 Models Only)

The fuel tank pressure sensor is tested using the GM Tech-1A® scan tool or equivalent. The sensor must be monitored and compared with pressure values using the EVAP system test port and the pressure tester. Follow the instructions included with the scan tool and/or use the guided diagnostics on the scan tool.

REMOVAL & INSTALLATION



Evaporative Emissions Canister

See Figures 6, 7, 8, 9, 10 and 11



Click image to see an enlarged view

Fig. Fig. 6: Remove the retaining bolts for the splash shield and ...



Click image to see an enlarged view

Fig. Fig. 7: ... remove the splash shield



Click image to see an enlarged view

Fig. Fig. 8: Remove the EVAP lines from the canister



Click image to see an enlarged view

Fig. Fig. 9: EVAP canister hose connections-1996-00 models



Click image to see an enlarged view

Fig. Fig. 10: Remove the retaining bolt from the canister bracket and ...



Click image to see an enlarged view

Fig. Fig. 11: ... slide the canister up and to the right to release the retaining tab and remove the canister

  1. Disconnect the negative battery cable.
  2.  
  3. Raise and safely support the vehicle securely on jackstands.
  4.  
  5. Remove the passenger side wheel well splash shield.
  6.  
  7. Tag and disconnect the hoses from the canister.
  8.  
  9. Remove the retaining bolt from the EVAP canister bracket and slide the canister up and to the right to release the retaining tab.
  10.  
  11. Remove the canister from the vehicle.
  12.  

Always replace any vapor hose(s) that may be showing signs of wear.

  1. Installation is the reverse of the removal procedure. Tighten the canister bracket retaining bolt to 6-9 ft. lbs. (8-12 Nm). Refer to the Vehicle Emission Control Information label, located in the engine compartment, for proper routing of the vacuum hoses.
  2.  

Canister Purge Control Solenoid Valve
1995-97 2.2L Engine

See Figure 12



Click image to see an enlarged view

Fig. Fig. 12: The EVAP canister purge solenoid is located under the intake manifold-2.2L engine

  1. Disconnect the negative battery cable.
  2.  
  3. Raise and safely support the vehicle securely on jackstands.
  4.  

The EVAP canister purge solenoid is located under the intake manifold and to the right and slightly above the ignition coils. It is accessible from underneath the vehicle.

  1. Tag and detach the electrical connector from the solenoid valve.
  2.  
  3. Remove the hoses from the purge solenoid.
  4.  
  5. Remove the purge solenoid from the mounting bracket.
  6.  
  7. If the solenoid mounting bracket needs to be removed, remove the retaining nut and remove the bracket.
  8.  
  9. Installation is the reverse of the removal procedure.
  10.  

1998-00 2.2L Engine and 2.3L/2.4L Engine

See Figures 13 and 14



Click image to see an enlarged view

Fig. Fig. 13: EVAP canister purge solenoid (2) mounting-1998-00 2.2L engine



Click image to see an enlarged view

Fig. Fig. 14: EVAP canister purge solenoid mounting-2.3L/2.4L engines

The purge solenoid is located on the valve cover on the 1998-00 2.2L engine and on the intake manifold, just above the A/C compressor on the 2.3L/2.4L engines.

  1. Disconnect the negative battery cable.
  2.  
  3. Detach the electrical connector from the solenoid valve.
  4.  
  5. Remove the hoses from the purge solenoid.
  6.  
  7. Remove the purge solenoid from the mounting bracket.
  8.  
  9. If the solenoid mounting bracket needs to be removed, remove the retaining nut and remove the bracket.
  10.  
  11. Installation is the reverse of the removal procedure.
  12.  

Tank Pressure Control Valve
  1. Tag and disconnect the hoses from the control valve.
  2.  
  3. Unfasten the mounting hardware.
  4.  
  5. Remove the control valve from the vehicle.
  6.  
  7. Installation is the reverse of the removal procedure. Refer to the Vehicle Emission Control Information label, located in the engine compartment, for proper routing of the vacuum hoses.
  8.  

Tank Pressure Sensor (199600 Models Only)

  1. Disconnect the negative battery cable.
  2.  
  3. Raise and safely support the vehicle securely on jackstands.
  4.  
  5. Remove the fuel tank assembly. Refer to Fuel System .
  6.  
  7. Release the retaining clip and remove the sensor from the tank.
  8.  

To install:
  1. Install the sensor into the tank and attach the retaining clip.
  2.  
  3. Install the fuel tank assembly.
  4.  
  5. Lower the vehicle.
  6.  
  7. Connect the negative battery cable.
  8.  

Vacuum Vent Valve (199600 Models Only)

  1. Disconnect the negative battery cable.
  2.  
  3. Raise and safely support the vehicle securely on jackstands.
  4.  
  5. Remove the passenger side wheel well splash shield.
  6.  
  7. Tag and disconnect the hose from the vent valve.
  8.  
  9. Remove the vent valve from the mounting bracket.
  10.  
  11. Installation is the reverse of removal.
  12.  

 
label.common.footer.alt.autozoneLogo