ISUZU Amigo/Pick-ups/Rodeo/Trooper 1981-1996

Evaporative Emission Controls

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OPERATION



See Figures 1, 2, 3 and 4



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Fig. Fig. 1: Evaporative emission system used on 1.8L and 2.0L engines



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Fig. Fig. 2: Evaporative emission system used on 2.6L fuel injected engines through 1995



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Fig. Fig. 3: Evaporative emission system used on 2.8L and 3.1L engines



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Fig. Fig. 4: Evaporative emission system used on 1996 3.2L engines-1996 2.6L engines are similar

To limit gasoline vapor discharge into the air, this system is designed to trap fuel vapors, which normally escape from the fuel tank and, if equipped, the carburetor. Vapor arrest is accomplished through the use of the charcoal canister. This canister absorbs fuel vapors and stores them until they can be removed to be burned in the engine. Removal of the vapors from the canister to the engine is accomplished by a carburetor, throttle body assembly or solenoid operated bowl vent. The fuel tank requires a non-vented gas cap. The domed fuel tank positions a vent high enough above the fuel to keep the vent pipe in the vapor at all times. The single vent pipe is routed directly to the canister. From the canister, the vapors are routed to the PCV system, where they will be burned during normal combustion.

TESTING



1.8L and 2.0L Engines
SYSTEM INSPECTION

Visually inspect the entire system for kinked, cracked, swollen, plugged or fatigued hoses. Replace the vapor canister if cracked, damaged or if fuel is leaking from the bottom.

CHECK AND RELIEF VALVE

See Figure 5



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Fig. Fig. 5: Check and relief valve operation

Remove the check valve and inspect for leakage by blowing air into the ports in the check valve as follows. Replace if necessary.

  1. When air is applied from the fuel tank side, the check valve is normal if air passes in to the check side (canister side), but not leaking into the relief side (air filter).
  2.  
  3. When air is applied from the check side, the valve is normal if air is restricted.
  4.  
  5. When air is applied from the relief side, the valve is normal if air passes into the fuel tank side but not into the check side.
  6.  

ROLL OVER AND FLOAT VALVE

Check the roll over and float valve for fuel leaks, distortion, dents and orifice clogging. Replace if necessary.

CANISTER

Remove the canister and inspect the function of the purge valve as follows. Replace if necessary.

  1. When 7.5 psi (51 kPa) of pressure is applied to the port marked VC , there should not be an air leak from the diaphragm.
  2.  
  3. Apply 15 in.Hg (50 kPa) of vacuum to the port marked PURGE . Gradually apply vacuum to the port marked VC .
  4.  
  5. If the purge control valve begins to open between 7-9 in.Hg (23-30 kPa), the purge control valve is normal.
  6.  

Carbureted 2.3L Engines
SYSTEM INSPECTION

Visually inspect the entire system for kinked, cracked, swollen, plugged or fatigued hoses. Replace the vapor canister if cracked, damaged or if fuel is leaking from the bottom.

CANISTER

Remove the canister and inspect the function of the purge valve as follows. Replace if necessary.

  1. When 7.5 psi (51 kPa) of pressure is applied to the port marked VC , there should not be an air leak from the diaphragm.
  2.  
  3. Apply 15 in.Hg (50 kPa) of vacuum to the port marked PURGE . Gradually apply vacuum to the port marked VC .
  4.  
  5. If the purge control valve begins to open between 7-9 in.Hg (23-30 kPa), the purge control valve is normal.
  6.  

VACUUM SWITCHING VALVE (VSV)

See Figure 6



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Fig. Fig. 6: VSV port identification

  1. Unplug the electrical connector. Using an ohmmeter check the resistance between the terminals. If should be approximately 35 ohms.
  2.  
  3. Using a fused jumper wire, apply battery voltage to the valve terminals.
  4.  
  5. Check to see that air does not flow freely through ports X and Y .
  6.  
  7. Remove the jumper wire from the terminals.
  8.  
  9. Check that air flows freely through ports X and Y . If a problem is found, replace the valve.
  10.  

VENTILATION VALVE

See Figure 7



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Fig. Fig. 7: Testing the ventilation valve

  1. Check to see that air flows freely through ports B and C .
  2.  
  3. Apply vacuum to port A . Check to see that air does not flow from ports B to C .
  4.  
  5. Replace the valve if defective.
  6.  

ROLL OVER AND FLOAT VALVE

Check the roll over and float valve for fuel leaks, distortion, dents and orifice clogging. Replace if necessary.

Fuel Injected 2.3L and 2.6L Engines
SYSTEM INSPECTION

Visually inspect the entire system for kinked, cracked, swollen, plugged or fatigued hoses. Replace the vapor canister if cracked, damaged or if fuel is leaking from the bottom.

CANISTER

See Figure 8



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Fig. Fig. 8: Canister port identification

This procedure does not apply to 1996 models. On 1996 models, visually inspect the canister. Replace the vapor canister if cracked, damaged or if fuel is leaking from the bottom.

  1. Unplug hose A from the canister. The hose should be free of restrictions and air should pass freely into the canister. Reconnect the hose.
  2.  
  3. Start the engine and allow it to idle.
  4.  
  5. Unplug hose C and and check that vacuum is not present at ports B and D .
  6.  
  7. Replace the canister if necessary.
  8.  

VACUUM SWITCHING VALVE (VSV)

See Figure 9



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Fig. Fig. 9: Testing the vacuum switching valve

This component is not used on 1996 models.

  1. Unplug the electrical connector. Using an ohmmeter check the resistance between the terminals. If should be approximately 35 ohms.
  2.  
  3. Using a fused jumper wire, apply battery voltage to the valve terminals.
  4.  
  5. Check to see that air does not flow freely through ports Y and Z , but flows freely from X to Y .
  6.  
  7. Remove the jumper wire from the terminals.
  8.  
  9. Check that air flows freely through ports Y and Z , but not X and Y . If a problem is found, replace the valve.
  10.  

PURGE VALVE

The purge valve is found on 1996 models only.

  1. Unplug the solenoid connector.
  2.  
  3. Disconnect the throttle body-to-purge solenoid vacuum hose.
  4.  
  5. Apply 15 in. Hg (51 kPa) of vacuum. The solenoid should hold vacuum; if not replace it.
  6.  
  7. Apply battery voltage to the solenoid terminals. The vacuum must drop. If not, replace the solenoid.
  8.  

2.8L and 3.1L Engines
SYSTEM INSPECTION

Visually inspect the entire system for kinked, cracked, swollen, plugged or fatigued hoses. Replace the vapor canister if cracked, damaged or if fuel is leaking from the bottom.

THERMOSTATIC VACUUM SWITCH
  1. Label and unplug the vacuum hoses from the switch on the intake manifold.
  2.  
  3. Make sure the coolant temperature is below 115°F (46°C). Apply vacuum to one of the switch ports. It should hold a vacuum.
  4.  
  5. Start the engine and observe the vacuum gauge as the coolant temperature reaches 115°F (46°C). When this temperature is approached, the switch should begin to bleed the vacuum.
  6.  
  7. Replace the switch if necessary.
  8.  

3.2L Engines
SYSTEM INSPECTION

Visually inspect the entire system for kinked, cracked, swollen, plugged or fatigued hoses. Replace the vapor canister if cracked, damaged or if fuel is leaking from the bottom.

PURGE VALVE
  1. Unplug the solenoid connector.
  2.  
  3. Disconnect the throttle body-to-purge solenoid vacuum hose.
  4.  
  5. Apply 15 in. Hg (51 kPa) of vacuum. The solenoid should hold vacuum; if not replace it.
  6.  
  7. Apply battery voltage to the solenoid terminals. The vacuum must drop. If not, replace the solenoid.
  8.  

PURGE VACUUM SWITCH

This is only used on 1996 3.2L engines.

  1. Unplug the solenoid connector.
  2.  
  3. Disconnect the purge solenoid-to-vacuum switch vacuum hose.
  4.  
  5. Using an ohmmeter, check for continuity between the ohmmeter terminals. If continuity is not present, replace the switch.
  6.  
  7. Apply vacuum to the switch. Continuity should not be present at the switch terminals. Replace the switch if necessary.
  8.  

PURGE VENT SOLENOID

This is only used on the 2.2L engine.

  1. Unplug the solenoid connector.
  2.  
  3. Unplug the vacuum hose from the canister leading to the vent solenoid.
  4.  
  5. Blow air through the hose. No air should pass.
  6.  
  7. Apply battery voltage to the solenoid terminals. Blow air through the hose. Air should pass through the filter.
  8.  

REMOVAL & INSTALLATION



Components of the evaporative system are all removed in the same basic manner. First label, then unplug any vacuum and electrical connections from the component. Remove any hardware retaining the component to the vehicle, then remove the component from the vehicle.

 
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