Nissan 240SX/Altima 1993-1998 Repair Guide

Evaporative Emission Controls

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OPERATION



See Figures 1, 2, 3 and 4



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Fig. Fig. 1: Evaporative emission control system schematic-1997-98 240SX



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Fig. Fig. 2: Evaporative emission control system schematic-1996 240SX



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Fig. Fig. 3: Evaporative emission control system schematic-1995 240SX and 1995-98 Altima



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Fig. Fig. 4: Evaporative emission control system schematic-1993-1994 240SX and Altima

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 (12,300 km).

COMPONENT TESTING



Evaporative Canister
ROUND CANISTER

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 Figure 5



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Fig. Fig. 5: Evaporative emission canister port identification-square canister

  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 6



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Fig. Fig. 6: 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 Figures 7 and 8



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Fig. Fig. 7: Evaporative canister purge volume control valve terminal testing locations



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Fig. Fig. 8: The plunger can be seen by looking through the side vacuum port

  1. Disconnect the valve electrical harness.
  2.  
  3. Measure resistance between terminals, as illustrated.
  4.  
  5. Resistance should be 30 ohms @ 44°F (22°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
  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
  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 Figures 9, 10 and 11



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Fig. Fig. 9: Purge control valve port identification-round canister



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Fig. Fig. 10: Connect a piece of vacuum hose to Port A and blow into it. If leaks are present, the valve is faulty



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Fig. Fig. 11: Next, connect a vacuum pump to the valve and apply vacuum. Blow into Port C and ensure that air flows out of Port B

  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 3.61-2.61 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 12



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Fig. Fig. 12: Purge control valve port identification-square canister

  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 8 psi pressure to Port A and hold for 9 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



Evaporative Canister
ROUND CANISTER

See Figure 13



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Fig. Fig. 13: The round canister is located on the firewall, below the fuel filter-Altima

The canister is located on the firewall (Altima) or the radiator support (27SX).

  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

See Figure 14



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Fig. Fig. 14: EVAP system components and location-square canister

  1. The canister is located on the firewall.
  2.  
  3. Label and disconnect the vacuum and vapor hoses.
  4.  
  5. Loosen the attaching bolts.
  6.  
  7. Carefully remove the canister from the vehicle.
  8.  
  9. Inspect the canister and lines for damage. Replace components as necessary.
  10.  
  11. Installation is the reverse of removal. Be sure to tighten the attaching bolts to 41-62 inch lbs. (5-8 Nm).
  12.  

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 9-8 ft. lbs. (10-13 Nm).
  2.  
  3. Connect the solenoid valve vacuum lines.
  4.  

Evaporative Canister Purge Volume Control Valve

See Figure 15



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Fig. Fig. 15: Evaporative canister purge volume control valve location

The evaporative canister purge volume control valve is located under the intake manifold.

  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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