Isuzu Cars and Trucks 1981-1991

Evaporative Canister

Print

To limit gasoline vapor discharge into the air this system is designed to trap fuel vapors, which normally escape from the fuel tank and 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. In addition to the carburetor modifications and the canister, 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.



Click image to see an enlarged view

Fig. Evaporative control system 4-cylinder gas engine



Click image to see an enlarged view

Fig. Evaporative control system V6 engine

SERVICING

Make sure the hoses are connected properly and not damaged.

FUNCTIONAL TEST V6 ONLY
Canister Purge Valve
  1. Apply a short length of hose to the lower tube of the purge valve and attempt to blow through the hose. Little or no air should pass through into the canister.
  2.  
  3. With a hand vacuum pump, apply 15 Hg (51 kPa) of vacuum through the control valve tube (upper tube). The diaphragm should hold vacuum for at least 20 seconds, if not the canister has to be replaced.
  4.  

Fuel Tank Pressure Control Valve
  1. Apply 15 Hg (51 kPa) of vacuum to the control vacuum tube. The diaphragm should hold vacuum for at least 20 seconds. If it does not, the diaphragm is leaking and the valve must be replaced.
  2.  
  3. With the vacuum applied to the control vacuum tube, apply a short hose to the valve's tank tube side and blow into the tube. The air should pass through the valve. If no air passes through the valve, the valve should be replaced.
  4.  

 
label.common.footer.alt.autozoneLogo