GM Caprice 1990-1993 Repair Guide

Evaporative Emission Controls

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See Figures 1, 2, 3 and 4



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Fig. Fig. 1: Evaporative Emission Control system - 5.0L (VIN Y) engine



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Fig. Fig. 2: Evaporative Emission Control system - except 5.0L (VIN Y) engine



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Fig. Fig. 3: Evaporative emission canister control valve - 5.0L (VIN Y) engines



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Fig. Fig. 4: Tank pressure control valve - except 5.0L (VIN Y) engine

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 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.

Carburetor models use an exhaust tube from the float bowl to the charcoal canister; fuel injected models eliminate the fuel bowl tube. 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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