GM Firebird 1982-1992 Repair Guide

Evaporative Emission Controls

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See Figures 1 through 8

OPERATION



This system reduces the amount of gasoline vapors escaping into the atmosphere. Some models employ a purge control solenoid which is controlled by the ECM, to open and close the EEC system. Other models use a canister mounted vacuum purge valve; when the engine vacuum reaches a certain pressure, the valve opens allowing the gas vapors to be drawn off to the carburetor for burning.

Carbureted models use an exhaust tube from the float bowl to the charcoal canister; fuel injected models eliminate the fuel bowl tube (as no float bowl is used on fuel injection systems). Fuel vapors from the gas tank travel from the tank to the vapor canister, where they are collected. Although the system varies from vehicle-to-vehicle, the operations are basically the same.



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Fig. Fig. 1: Evaporative Emission Control (EEC) System-2.5L engines



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Fig. Fig. 2: EEC system-2.8L carbureted engines



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Fig. Fig. 3: EEC system on TPI and TBI V6/V8 engines



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Fig. Fig. 4: EEC system on carbureted V8 engines

TESTING



Tank Pressure Control Valve
  1. Using a hand-held vacuum pump, apply a vacuum of 15 in. Hg. (51 kPa) through the control vacuum signal tube to the purge valve diaphragm. If the diaphragm does not hold 5 in. Hg. at least for 10 seconds, the diaphragm is leaking. Replace the control valve.
  2.  



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Fig. Fig. 5: Compression gauge and a combination vacuum/fuel pressure test gauge

  1. With the vacuum still applied to the control vacuum tube, attach a short piece of hose to the valve's tank tube side and blow into the hose. Air should pass through the valve. If it does not, replace the control valve.
  2.  

REMOVAL & INSTALLATION



Canister
  1. Disconnect the negative battery cable.
  2.  
  3. Loosen the screw holding the canister retaining bracket.
  4.  
  5. Remove the canister.
  6.  
  7. Tag and disconnect the hoses leading from the canister.
  8.  

To install:
  1. Connect the hoses to the canister according to the tags.
  2.  
  3. Install the canister into the retaining bracket.
  4.  
  5. Tighten the screw holding the canister retaining bracket.
  6.  
  7. Reconnect the negative battery cable.
  8.  



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Fig. Fig. 6: A common EEC canister location



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Fig. Fig. 7: Be sure to label the hoses before disconnecting them to avoid confusion later

Filter

Not all models use canisters with replaceable filters.

  1. Remove the vapor canister.
  2.  
  3. Pull the filter out from the bottom of the canister.
  4.  
  5. Install a new filter and then replace the canister.
  6.  

Canister Purge Solenoid

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the bolt, cover and solenoid.
  4.  
  5. Disconnect the electrical wiring and hoses from the solenoid.
  6.  
  7. Remove the solenoid.
  8.  

To install:
  1. Install the solenoid, cover and bolt.
  2.  
  3. Connect the hoses and electrical wiring solenoid.
  4.  
  5. Connect the negative battery cable.
  6.  



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Fig. Fig. 8: A common canister purge solenoid location

Tank Pressure Control Valve
  1. Disconnect the hoses from the control valve.
  2.  
  3. Remove the mounting hardware.
  4.  
  5. Remove the control valve from the vehicle.
  6.  
  7. Installation is the reverse of the removal procedure. Refer to the Vehicle Emission Control Information (VECI) label, located in the engine compartment (if present) or the diagrams found later in this section, for proper routing of the vacuum hoses.
  8.  

 
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