Nissan Maxima 1993-1998 Repair Guide

Evaporative Emission Controls

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OPERATION



See Figure 1



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Fig. Fig. 1: Schematic view of the evaporative emission system

The evaporative emission control system prevents the uncontrolled release of gasoline vapors (hydrocarbons) into the atmosphere. These vapors are produced when fuel evaporates in the sealed fuel tank..

The main component of the system is the charcoal canister. The activated charcoal in the canister absorbs and stores fuel vapors generated inside the fuel tank while the engine is inoperative. When the engine is running, the vapors are drawn through the electronically controlled purge control valve and into the intake manifold. The vapors enter the air/fuel mixture and are burned in the combustion process.

Not all components are used on all vehicles.

The purge control valve is used to time the vapor release into the intake manifold. During deceleration and idling, the purge control valve is closed and allows only a small amount of vapor to reach the intake. Under all other conditions, the valve allows vapor to be purged.

Two types of purge control valves are used: an electronic canister purge volume control valve and a purge control valve/constant purge orifice combination. The canister purge volume valve is controlled by the ECM and meters purge volume in proportion to air flow. The purge control valve/constant purge orifice combination operates mechanically. As engine speed increases and throttle vacuum rises, more vapor is purged to the intake manifold.

The canister control solenoid valve responds to signals from the ECM. When the ECM grounds the solenoid, the vacuum signal from the throttle body to the canister is cut. Generally, this is done under start-up, idling and decelerating conditions.

A fuel check valve (vacuum cut valve) is used to prevent engine vacuum from sucking fuel out of the fuel tank. The valve also functions to prevent fuel from flowing out of the fuel tank if the vehicle should roll over.

The fuel cap contains a vacuum relief valve which allows air into the fuel tank to prevent a build-up of vacuum.

The evaporative emission system canister, vacuum line and vapor hoses should be inspected every 30,000 miles (48,300 km).

COMPONENT TESTING



Evaporative Canister

On all 1993-95 models, the canister is located under the battery, except the 1995 California model, which has a square canister under the left rear fender. All 1996-98 models use the square canister under the left rear fender.

ROUND CANISTER

See Figure 2



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Fig. Fig. 2: Round evaporative canister inspection diagram

  1. Refer to the illustration for port identification.
  2.  
  3. Blow air into port A and check for any leakage.
  4.  
  5. Use a vacuum pump and apply vacuum to port A.
  6.  
  7. Using a free hand, cover port D while blowing air into port C; air should flow out of port B.
  8.  

The round evaporative canister is a sealed component and cannot be disassembled for inspection. Visually inspect the exterior of the canister for damage and replace as necessary.

SQUARE CANISTER

See Figures 3 and 4



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Fig. Fig. 3: Evaporative emission canister port identification-square canister



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Fig. Fig. 4: Evaporative hose detail

  1. Visually inspect the exterior of the canister for damage, and replace as necessary.
  2.  
  3. Label and disconnect all vacuum and vapor lines.
  4.  
  5. Inspect the lines for damage, and replace as necessary.
  6.  
  7. Inspect the canister for damage, and replace as necessary.
  8.  
  9. Pinch the fresh air vent hose.
  10.  
  11. Blow air in Port A and check that it flows freely out of Port E .
  12.  
  13. If air does not flow as specified, the canister may be defective.
  14.  

Evaporative Canister Control Solenoid Valve

See Figure 5



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Fig. Fig. 5: Evaporative canister control solenoid valve terminal and port identification

This valve may be known as the canister purge control valve on some vehicles.

  1. Label and disconnect the vacuum lines and electrical harness.
  2.  
  3. Inspect the lines for damage, and replace as necessary.
  4.  
  5. Inspect the valve for damage, and replace as necessary.
  6.  
  7. Apply battery voltage and ground between the valve terminals.
  8.  
  9. Air should pass between Port A and Port B .
  10.  
  11. Air should not pass between Port A and Port C .
  12.  
  13. Remove battery voltage.
  14.  
  15. Air should pass between Port A and Port C .
  16.  
  17. Air should not pass between Port A and Port B .
  18.  
  19. If valve does not function as specified, it may be faulty.
  20.  
  21. If the valve responds as specified, check and repair power and ground circuits.
  22.  

Evaporative Canister Purge Volume Control Valve

See Figure 6



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Fig. Fig. 6: Evaporative canister purge volume control valve terminal testing locations

  1. Disconnect the valve electrical harness.
  2.  
  3. Measure resistance between terminals, as illustrated.
  4.  
  5. Resistance should be 30 ohms at 77°F (25°C).
  6.  
  7. Remove the valve from the intake collector and disconnect the vacuum hoses.
  8.  
  9. With the electrical harness connected, cycle the ignition key ON and OFF .
  10.  
  11. Visually inspect the plunger in the valve for movement. The plunger can be seen by looking through the side vacuum port.
  12.  
  13. If resistance is not within specification or the valve does not move freely, the valve may be defective.
  14.  
  15. If the valve functions as specified, check and repair the power and ground circuits.
  16.  

Fuel Cap

See Figure 7



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Fig. Fig. 7: The fuel tank vacuum relief valve is located in the fuel cap

  1. Wipe the valve housing clean.
  2.  
  3. Suck air through the cap using a vacuum pump and the proper adapters supplied with the pump.
  4.  
  5. A slight resistance accompanied by valve clicks indicates that the valve is in good mechanical condition.
  6.  

By continually sucking air through the cap, the resistance should disappear.

  1. Blow air through the fuel tank side of the cap and ensure that air passes through the cap.
  2.  
  3. If the valve in the cap is clogged or if no resistance is felt, replace the cap as an assembly.
  4.  

Fuel Check Valve

See Figure 8



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Fig. Fig. 8: The fuel tank vent check valve also acts as a safety valve in the event of a vehicle rollover

  1. Remove the valve from the vehicle.
  2.  
  3. Blow air through the nipple on the fuel tank side.
  4.  
  5. A considerable resistance should be felt and a portion of the air flow should be directed toward the canister side nipple.
  6.  
  7. Blow air through the nipple on the canister side.
  8.  
  9. Air flow should be smoothly directed toward the fuel tank side.
  10.  
  11. Turn the valve over and blow air through either nipple.
  12.  
  13. Air should not flow in either direction.
  14.  
  15. If the valve does not function as specified, it may be faulty.
  16.  

Purge Control Valve
ROUND CANISTER

See Figure 9



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Fig. Fig. 9: Purge control valve port identification

  1. Label and disconnect all vacuum and vapor lines.
  2.  
  3. Inspect the lines for damage, and replace as necessary.
  4.  
  5. Inspect the canister for damage, and replace as necessary.
  6.  
  7. Blow air in Port A and ensure that there is no leakage.
  8.  
  9. Apply a 3.94-5.91 in. Hg vacuum to port A .
  10.  
  11. Cover Port D with your hand.
  12.  
  13. Blow air into Port C and verify that there is a free flow of air out of Port B .
  14.  
  15. If air does not flow as specified, the canister may be defective.
  16.  

SQUARE CANISTER

See Figure 10



Click image to see an enlarged view

Fig. Fig. 10: Purge control valve port identification

  1. Label and disconnect all vacuum and vapor lines.
  2.  
  3. Inspect the lines for damage, and replace as necessary.
  4.  
  5. Inspect the valve for damage, and replace as necessary.
  6.  
  7. Plug Port B .
  8.  
  9. Apply an 11 psi pressure to Port A and hold for 15 seconds.
  10.  
  11. Ensure that there is no leakage.
  12.  
  13. Repeat the test for Port C .
  14.  
  15. If leakage occurs, the valve may be defective.
  16.  

REMOVAL & INSTALLATION



On all 1993-95 models, the canister is located under the battery, except the 1995 California model, which has a square canister under the left rear fender. All 1996-98 models also use the square canister under the left rear fender.

Evaporative Canister
ROUND CANISTER
  1. Label and disconnect the vacuum and vapor lines.
  2.  
  3. Loosen the attaching bolts.
  4.  
  5. Carefully remove the canister from the vehicle.
  6.  
  7. Inspect the canister and lines for damage. Replace components as necessary.
  8.  
  9. Installation is the reverse of removal. Be sure to tighten the attaching bolts securely.
  10.  

SQUARE CANISTER
  1. Label and disconnect the vacuum and vapor hoses.
  2.  
  3. Loosen the attaching bolts.
  4.  
  5. Carefully remove the canister from the vehicle.
  6.  
  7. Inspect the canister and lines for damage. Replace components as necessary.
  8.  
  9. Installation is the reverse of removal. Be sure to tighten the attaching bolts to 74-95 inch lbs. (8-11 Nm).
  10.  

Evaporative Canister Control Solenoid Valve

The evaporative canister control solenoid valve is located on the intake manifold.

  1. Label and disconnect the solenoid valve vacuum lines.
  2.  
  3. Loosen the solenoid valve attaching nut, then separate the valve from the intake manifold.
  4.  

To install:
  1. Install the solenoid valve and tighten the mounting nut to 12-14 ft. lbs. (16-19 Nm).
  2.  
  3. Connect the solenoid valve vacuum lines.
  4.  

Evaporative Canister Purge Volume Control Valve
  1. Label and disconnect the vacuum lines and electrical harnesses.
  2.  
  3. Inspect the lines for damage, and replace as necessary.
  4.  
  5. Remove the valve from the intake collector.
  6.  

To install:
  1. Inspect valve for damage, and replace as necessary.
  2.  
  3. Install the valve on the collector.
  4.  
  5. Connect the vacuum lines and electrical harness.
  6.  

Fuel Check Valve

The fuel check valve is located in the vapor vent line near the fuel tank.

  1. Raise and support the vehicle safely.
  2.  
  3. Locate the valve in the vapor vent line.
  4.  
  5. Note the installed direction of the valve for installation reference.
  6.  
  7. Loosen the hose clamps and remove the valve.
  8.  
  9. Installation is the reverse of removal.
  10.  

Purge Control Valve
ROUND CANISTER

On round canisters, the purge control valve is an integral part of the evaporative canister. If the valve is determined to be faulty, the canister and purge control valve must be replaced as an assembly.

SQUARE CANISTER

On square canisters, the purge control valve is a separate component mounted near the canister, at the rear of the vehicle.

  1. Label and disconnect the vacuum and vapor lines.
  2.  
  3. Inspect the lines for damage, and replace as necessary.
  4.  
  5. Remove the valve from the vehicle.
  6.  

To install:
  1. Inspect the valve for damage, and replace as necessary.
  2.  
  3. Install the valve on the vehicle.
  4.  
  5. Connect the vacuum lines.
  6.  

 
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