Pontiac Fiero 1984-1988 Repair Guide

Evaporative Emission Control System

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OPERATION





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Fig. Fig. 1 Schematic of the evaporative system used on 2.5L engines



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Fig. Fig. 2 Location of the evaporator canister and its related components-2.8L engines



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Fig. Fig. 3 Schematic of the evaporative system used on the 2.8L engine

This method transfers fuel vapor from the fuel tank to an activated carbon (charcoal) storage canister to hold the vapors when the vehicle is not operating. When the engine is running, the fuel vapor is purged from the carbon element by intake air flow and consumed in the normal combustion process.

The vapor canister uses a integral diaphragm operated purge valve. When the engine is running, manifold vacuum is supplied to the top tube of the purge valve, the valve opens and the vapor is pulled into the throttle body or air plenum.

SERVICE



Evidence of fuel loss or fuel vapor odor can be caused by the following:

  1. Liquid fuel leaking from the fuel lines or throttle body.
  2.  
  3. Inoperative purge valve.
  4.  
  5. Disconnected or damaged vapor and control lines.
  6.  
  7. Air cleaner or cleaner gasket improperly seated.
  8.  

Poor idle, stalling or poor driveability can be caused by the following:

  1. Inoperative purge valve.
  2.  
  3. Damaged canister.
  4.  
  5. Hoses split, cracked, damaged or connected improperly.
  6.  

TESTING



  1. Visually check the canister for cracks or damage, replace canister.
  2.  
  3. If fuel is leaking from the bottom of the canister, replace canister and check for proper hose routing.
  4.  
  5. Check the filter at the bottom of the canister. If dirty, replace the filter.
  6.  
  7. Functional test the purge valve by installing a piece of hose to the lower tube of the valve and attempt to blow through it. Little or no air should pass into the canister.
  8.  
  9. Connect a vacuum pump and apply 15 Hg (51 kPa) of vacuum to the upper control valve tube. The diaphragm should hold vacuum for at least 20 seconds. If it does not hold vacuum, the canister must be replaced.
  10.  

REMOVAL & INSTALLATION



  1. Disconnect the negative (-) battery cable.
  2.  
  3. Remove the hoses on the canister and mark them for installation.
  4.  
  5. Remove the canister bracket attaching bolt.
  6.  
  7. Install the canister and torque the attaching bolt to 6-9 ft. lbs. (8-12 Nm). Reconnect the hoses in their original locations.
  8.  
  9. Start the engine and check for proper operation and fuel leaks.
  10.  

 
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